Exhibit 4.56







|5 May 2015 | 
|---------- | 







Strictly Private & Confidential



Julian Gangolli





Dear Julian,



In addition to your offer letter, which sets
out the elements of our employment offer, I am now writing to summarize the discretionary/non-contractual benefits that you would
be eligible to receive during your employment at GW Pharmaceuticals Inc (the “Company”).



A summary of the discretionary/non-contractual
benefits for this role is outlined below:



| | · | As the Company does not currently have
a healthcare benefits program established, and in the event that you do not wish to continue with coverage paid by your former
employer, we will reimburse you reasonable costs of your medical premiums so you can establish your own health insurance coverage.
Once the Company’s medical benefits program is established, this contribution will cease and you will be eligible to enroll
in the company benefits program.
| | - | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------



| | · | It is also our intent to establish a Death-In-Service
life insurance. This benefit would be fully paid for by the Company on your behalf.
| | - | -----------------------------------------------------------------------------------------------------------------------------------------



| | · | It is our intent to establish a 401K Plan
for our employees as soon as possible. Once established, you will be eligible to enroll in the program and receive the Company’s
matching contribution.
| | - | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------



As soon as these, and other benefit programs,
are established, enrollment and participation details will be communicated to all employees of the Company.



You will be entitled to seek reimbursement
of all business expenses that you incur, including the costs of maintaining a business telephone line, mobile phone, etc., in accordance
with our US Travel and Expense Policy.



In addition to the above benefits you will
be entitled to participate in the discretionary GW Pharmaceuticals group long term incentive and bonus scheme as follows:











| | · | You will, in addition to your salary, be eligible for a discretionary bonus. In accordance with
the remuneration policy approved by the Company’s shareholders, the terms and amount of this bonus will be decided from time
to time by the Remuneration Committee in its sole discretion.
| | - | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------



| | · | As soon as possible after the date of commencement
of employment (subject to any close period restrictions), and subject to ratification from the Remuneration Committee, the Company
will grant you equity-based incentives equivalent to 4.5 X salary ($1.8m) through 3 instruments:
| | - | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------



-              25% as Restricted Stock
Awards



These awards vest evenly over a
4 year period, based solely on employment. They represent shares exercised at nominal par value (0.1p), hence the recipient retains
full value of shares at the market price at the time of vesting.



-              50% as Performance Stock
Units



These awards vest after 3 years
and are dependent on specific company performance criteria. They represent shares exercised at nominal par value (0.1p), hence
the recipient retains the full value of the shares at the market price at the time of vesting.



It is expected that 50% of these
PSUs will vest upon submission of an NDA to the FDA for Epidiolex, and that the remaining 50% will vest upon achievement of FDA
approval for Epidiolex. Although these proposed performance conditions have been discussed with the Remuneration Committee, the
Committee has the discretion to revise these performance conditions at the time of the awards being granted to you.



-              25% as Market Price Options



These awards vest after 3 years’
service. Exercise price equals the market price at grant, hence value linked to share price growth between grant of option and
vesting period



The number of shares will be based on Black
scholes valuations (or similar appropriate valuation method) of each option type on the date of grant.



At the end of each calendar year, subject to
satisfactory personal and company performance, you may be eligible to receive additional grants of equity-based incentives



All of the above benefits remain entirely at
the discretion of the Company and may change from time to time.



We are all delighted that you are joining us
and look forward to working with you.











Sincerely,



/s/ Justin Gover



Justin Gover

Chief Executive Officer