Exhibit 4.61







1 January 2016



Mr Cabot Brown



Dear Cabot



GW Pharmaceuticals plc (the "Company")



I am writing to record the amended terms of
your appointment as a non-executive Director of, GW Pharmaceuticals plc ("GW"). These amended termswill
take effect on 1 January 2016 and will continue until terminated by either party giving to the other not less than 3 months' prior
written notice or as provided for in paragraph 1 below.



The terms of appointment replace the previous
terms of you appointment by GW Pharmaceuticals Inc. dated 7 November 2013. Your employment by GW Pharmaceuticals Inc. ended on
31 December 2015.



| | 1. | Appointment
| | -- | -----------



| | (a) | Your appointment as a non-executive Director of GW is subject to the Articles of Association of
GW. Your appointment as a Director will be subject to the usual rules requiring your appointment and re-appointment to be approved
by shareholders. Your appointment as a non-executive Director will automatically terminate without any entitlement to compensation
if you:
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| | (i) | are removed from office by a resolution of the shareholders;
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| | (ii) | are not re-elected to office; or
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| | (iii) | cease to be a director by reason of your vacating office pursuant to any provision of the Company's Articles of Association.
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| | (b) | The Company may terminate your appointment with immediate effect if you:
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| | (i) | commit any act, whether or not in the course of your duties for the Company, which tends to bring you or the Company or Group
into disrepute;
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| | (ii) | commit a material breach of your obligations under this
letter;
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| | (iii) | commit any serious or repeated breach or non-observance of your obligations to the Company (which include an obligation not
to breach your duties to the Company, whether statutory, fiduciary or common law);
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| | (iv) | are declared bankrupt or have made an arrangement with, or for the benefit of, your creditors;
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| | (v) | are convicted of any arrestable criminal offence (other than an offence under road traffic legislation in the UK or elsewhere
for which a fine or non-custodial penalty is imposed); or
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| | (vi) | are unavailable to perform your duties under your appointment for 6 months consecutively or in aggregate in any period of one
year.
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| | (c) | During any period of notice in accordance with this agreement, the Company may at its absolute
discretion ask you not to attend any Board or General meetings or to perform any other services on its behalf.
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| | (d) | Non-executive directors on the GW Board are typically expected to serve two three-year terms but
you may be invited by the Company to serve for an additional period on the Board. Any term renewal is subject to Board review and
GW AGM re-election. Notwithstanding any mutual expectation, there is no right to re-nomination by the Board, either annually or
after any three-year period.
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| | (e) | Upon the ending of your appointment for any reason, you will resign at the request of the Company,
without any claim for compensation (other than for accrued and unpaid fees due under this letter), from all directorships and other
offices held by you in the Company and any other member of the Group and from all trusteeships held by you of any pension scheme
or other trusts established by any member of the Group. Should you fail to do so, you irrevocably appoint any member of the Board
as your attorney in your name and on your behalf to sign any documents and take such other steps as are necessary to give effect
to those resignations.
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| | 2. | Time commitment
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| | (a) | You will be expected to devote such time, in the UK, as is necessary for the proper performance
of your duties, and you should be prepared to spend at least 12 days per annum attending meetings representing the Company business
interests. You are expected to attend GW Board Meetings and GW General Meetings of the shareholders of GW as and when they are
held. In connection with attendance at the meetings, you will exercise such functions that are specifically delegated to you from
time to time by the Board.
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| | (b) | You will be required to sit on the Remuneration Committee, the Nomination Committee and the Audit
Committee of the GW Board.
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| | (c) | We expect this role to involve attendance at six GW Board meetings, the GW Annual General Meeting,
GW Audit committee meetings with auditors and occasional attendance, as required, and meetings with other advisers and shareholders.
Unless urgent and unavoidable circumstances prevent you from doing so, it is expected that you will attend these meetings, to be
held in the UK.
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| | (d) | Additional time may be required, on an ad-hoc basis, to attend meetings to deal with certain GW
Board and sub-committee matters as they arise. The nature of the role makes it impossible to be specific about the maximum time
commitment, and there is always the possibility of additional time commitment in respect of preparation time and ad hoc matters
which may arise from time to time, and particularly when the Company is undergoing a period of increased activity. At certain times,
it may be necessary to convene additional GW Board, committee or shareholder meetings.
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| | (e) | In accepting this role you are deemed to undertake that you have sufficient time available to commit
to the proper performance of this role. Prior to acceptance of the role you will be required to provide to the Company Secretary
details of your other Board appointments and significant commitments with a broad indication of the time involved and will be required
to update the Company Secretary from time to time of any changes to these commitments.
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| | 3. | Remuneration and expenses
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| | (a) | Your fees will be $70,000 per annum, and will be subject to any deduction required by law. This
will be paid monthly in arrears. You are not eligible for any other benefits.
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| | (b) | This fee will be reviewed from time to time by the GW Board. It is our current practice to review
these fees at the end of each calendar year although such review does not imply nor guarantee any increase.
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| | (c) | You will not be entitled to participate in any Group pension scheme
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| | (d) | You will be reimbursed for all reasonable out-of-pocket expenses properly incurred by you on Company
business, including costs associated with you attending UK Board, Committee and General Meetings. Reimbursement would include the
reasonable cost of obtaining legal advice, if circumstances should arise where it was necessary for you to seek such advice separately,
about your responsibilities as a non-executive director of the Company although you should initially raise any such concerns with
the Chairman of the Company. This advice should be obtained, and reimbursement will only be made, in accordance with any formal
procedure for directors to take independent professional advice adopted from time to time by the Company and a copy of the current
version will be supplied to you. Claims for reimbursement should be accompanied by evidence of expenditure.
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| | 4. | Insurance
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The Company will,
at its expense, provide you with director's and officer's liability insurance, subject to the provisions governing such insurance
and on such terms as the Board may from time to time decide (including but not limited to terms relating to the level of cover,
deductibles, caps, exclusions and aggregate limits) and subject to the obtaining of insurance at reasonable rates of premium. No
undertaking is given regarding the continuation of this insurance, other than that you will be covered for as long as it remains
in place for the directors of the Company.



| | 5. | Duties
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| | (a) | You will be expected to perform your duties, whether statutory, fiduciary or common-law, faithfully,
efficiently and diligently to a standard commensurate with both the functions of your role and your knowledge, skills and experience.
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| | (a) | You will exercise your powers in your role as a non-executive director having regard to relevant
obligations under prevailing law and regulation, including the Companies Act 2006. You are also required to comply with the requirements
of Nasdaq. You will be advised by the Company Secretary where these differ from requirements in the UK.
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| | (b) | You will have particular regard to the general duties of directors as set out in Part 10, Chapter
2 of the Companies Act 2006, including the duty to promote the success of the company:
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"A director
of a company must act in the way he considers, in good faith, would be most likely to promote the success of the company for the
benefit of its members as a whole, and in doing so have regard (amongst other matters) to -



| | (a) | the likely consequences of any decision in the long term,
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| | (b) | the interests of the company's employees,
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| | (c) | the need to foster the company's business relationships with suppliers, customers and others,
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| | (d) | the impact of the company's operations on the community and the environment,
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| | (e) | the desirability of the company maintaining a reputation for high standards of business conduct,
and
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| | (f) | the need to act fairly as between members of the company."
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| | (c) | In your role as non-executive director you will be required to:
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| | · | constructively challenge and help develop proposals on strategy;
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| | · | scrutinise the performance of management in meeting agreed goals and objectives and monitor the
reporting of performance;
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| | · | satisfy yourself on the integrity of financial information and that financial controls and systems
of risk management are robust and defensible;
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| | · | determine appropriate levels of remuneration of executive directors and have a prime role in appointing
and, where necessary, removing executive directors, and in succession planning;
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| | · | devote time to developing and refreshing your knowledge and skills;
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| | · | uphold high standards of integrity and probity and support me and the other directors in instilling
the appropriate culture, values and behaviours in the boardroom and beyond;
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| | · | insist on receiving high-quality information sufficiently in advance of board meetings; and
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| | · | take into account the views of shareholders and other stakeholders where appropriate.
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| | (d) | You will be required to exercise relevant powers under, and abide by, GW’s articles of association.
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| | (e) | You will be required to exercise your powers as a director in accordance with GW’s policies
and procedures.
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| | (f) | You will disclose any direct or indirect interest which you may have in any matter being considered
at a board meeting or committee meeting and, save as permitted under the articles of association, you will not vote on any resolution
of the Board, or of one of its committees, on any matter where you have any direct or indirect interest.
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| | (g) | You will immediately report to the Chairman your own wrongdoing or the wrongdoing or proposed wrongdoing
of any employee or director of which you become aware.
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| | (h) | Unless specifically authorised to do so by the Board, you will not enter into any legal or other
commitment or contract on behalf of the Company.
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| | 6. | Outside interests
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During your appointment
you may not, without the prior approval of the Board, accept a directorship of a company or provide your services to anyone who
is a competitor of the Group. The Board's agreement will not be given if such appointment or involvement would conflict with or
is likely to interfere with this appointment. It is the parties understanding that the definition of a competitor shall be restricted
to a project, business or activity, directly or indirectly, involving cannabinoid research. Please let the Company Secretary have
a list of your current commitments for our records and keep him updated in that respect.



| | 7. | Confidentiality
| | -- | ---------------



You should not,
during your appointment (except in the proper performance of your duties and then only to those who need to know such information)
or after it has ceased (except as required by law), disclose to any person, company or other organisation or use otherwise than
for the benefit of the Group any confidential information or trade secrets concerning its business. This includes but is not limited
to:



| | (a) | corporate and marketing strategy, acquisition and investment proposals, business development and
plans, maturing business opportunities, sales reports and research results;
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| | (b) | business contacts, lists of customers and suppliers and details of contracts with customers and
suppliers and their current or future requirements;
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| | (c) | budgets, financial plans and management accounts, trading statements and other financial reports
and information;
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| | (d) | unpublished price sensitive information about the Group; and
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| | (e) | any document marked "confidential" and any information which by its nature is commercially
sensitive.
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| | 8. | Compliance
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| | (a) | You are expected to comply with the Company's articles of association, the City Code on Takeovers
and Mergers, applicable stock exchange rules and regulations and the Company's relevant internal codes. In particular during your
appointment you will comply, and will procure, so far as you are able, that your spouse or Civil Partner and dependent children
(if any) or any trust in which you or your spouse or Civil Partner may be concerned or interested as trustee or beneficiary, comply
with any code of conduct relating to securities transactions by directors and specified employees adopted by the Company from time
to time.
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| | (b) | You will promptly give the Company such information as the Company or any member of the Group may
require to enable it to comply with its legal and regulatory obligations whether to any securities or investment exchange or regulatory
or governmental body to which any member of the Group is, from time to time, subject or howsoever arising.
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| | 9. | Return of Company property
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When your appointment
ends, you should, unless otherwise agreed in writing, immediately return all documents and other property belonging to any member
of the Group and which may be in your possession or under your control. No copies (including electronic copies) should be retained
by you or by anyone on your behalf.



| | 10. | Data protection
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By signing this
letter you consent to the Company holding and processing information about you for legal, personnel, administrative and management
purposes and in particular to the processing of any sensitive personal data (as defined in the Data Protection Act 1998) including,
as and when appropriate:



| | (i) | information about your physical or mental health or condition
in order to monitor sick leave and take decisions as to your fitness to perform your duties;
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| | (ii) | information about you that may be relevant to ensuring equality of opportunity and treatment in line with the Company’s
equal opportunities policy and in compliance with equal opportunities legislation; and
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| | (iii) | information relating to any criminal proceedings in which you have been involved, for insurance purposes and in order to comply
with legal requirements and obligations to third parties.
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You consent to
the transfer of such personal information to any member of the Group (or a company appointed by them for such purposes), whether
or not outside the European Economic Area, for administration purposes and other purposes in connection with your appointment,
where it is necessary or desirable for the Company to do so.











| | 11. | Non-compete
| | --- | -----------



In consideration
for the fees payable to you under this letter, you agree you will not (except with prior written consent of the GW Board) directly
or indirectly do or attempt to, for the period of 12 months immediately after the termination of your office, to any material extent,
undertake, carry on or be employed, engaged or interested in any capacity in the supply or proposed supply of Competitive Services
within the Territory. For the purposes of this paragraph, "Competitive Services" means any business connected to the
marketing, sales or distribution, or development or proposed development of pharmaceuticals from cannabinoids which is competitive
with the Company's or GW, or GW Pharma's businesses; and "Territory" means England, Wales, Scotland and/or Northern Ireland
and any other country, or, in the United States, any state, which the Company or any member of the Group is operating or planning
to operate a competitive business at the end of your appointment.



| | 12. | Rights of third parties
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The Contracts (Rights
of Third Parties) Act 1999 shall not apply to this letter. No person other than you and the Company shall have any rights under
this letter and the terms of this letter shall not be enforceable by any person other than you and the Company.



| | 13. | Miscellaneous
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| | (a) | For the purpose of this letter:
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the "Board"
shall mean the board of directors of the Company as constituted from time to time;



"Civil Partner"
means a civil partner as defined by the Civil Partnership Act 2004; and



the "Group"
means any of the following from time to time: the Company, its subsidiaries and subsidiary undertakings and any holding company
or parent undertaking of the Company and all other subsidiaries and subsidiary undertakings of any holding company or parent undertaking
of the Company, where "holding company", "parent undertaking", "subsidiary" and "subsidiary
undertaking" have the meanings given to them in the Companies Act 2006.



| | (b) | This letter will be construed in accordance with English law and you and the Company irrevocably
submit to the exclusive jurisdiction of the English Courts to settle any dispute which may arise in connection with this letter.
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| | (c) | This letter constitutes the entire terms and conditions of your appointment. No variation or addition
to this letter and no waiver of any provision of it will be valid unless in writing and signed by or on behalf of both parties.
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I would ask you to countersign the enclosed
copy of this letter to confirm the basis of your appointment with the Company and to show acceptance of the terms of this letter
by executing it as a deed.



I look forward to continuing to work with you
to the general benefit of our shareholders.



Yours sincerely



/s/ Adam George



Adam George



For and on behalf of the Board of Directors
of GW Pharmaceuticals plc



Signed as a Deed by:



|/s/ Cabot Brown | Date | 2/4/16
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in the presence of :



|Witness:    | /s/ Adam George               | 
|----------- | ----------------------------- | 
|            |                               | 
|Name:       | Adam George                   | 
|            |                               | 
|Address:    | c/o 1 Cavendish Place, London | 
|            |                               | 
|Occupation: | Chief Financial Officer       |