##### 



Exhibit 4(a)




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##### 



PageARTICLE I THE MERGER
    
    
    21.1.
    
    Effective Time of the Merger
    
    
    21.2.
    
    Closing
    
    
    31.3.
    
    Effects of the Merger
    
    
    31.4.
    
    Certificate of Incorporation and By-Laws
    
    
    31.5.
    
    Directors and Officers
    
    
    4ARTICLE II EFFECT OF THE MERGER ON
THE CAPITAL STOCK OF THE CONSTITUENT CORPORATIONS; SURRENDER
        OF CERTIFICATES
    
    
    52.1.
    
    Effect on Capital Stock
    
    
    52.2.
    
    Surrender of Certificates
    
    
    6ARTICLE III REPRESENTATIONS AND WARRANTIES
    
    
    123.1.
    
    Representations and Warranties of KeySpan
    
    
    123.2.
    
    Representations and Warranties of Parent and Merger Sub
    
    
    13ARTICLE IV COVENANTS RELATING TO CONDUCT OF BUSINESS
    
    
    134.1.
    
    Covenants of KeySpan
    
    
    134.2.
    
    Covenants of Parent
    
    
    134.3.
    
    Advice of Changes; Governmental Filings
    
    
    134.4.
    
    Transition Planning
    
    
    134.5.
    
    Control of Other Partys Business
    
    
    13ARTICLE V ADDITIONAL AGREEMENTS
    
    
    135.1.
    
    Preparation of Proxy Statement and Circular; Stockholders Meetings
    
    
    135.2.
    
    Corporate Governance
    
    
    135.3.
    
    Access to Information
    
    
    135.4.
    
    Reasonable Best Efforts
    
    
    135.5.
    
    No Solicitation by KeySpan
    
    
    135.6.
    
    KeySpan Stock Options and Other Stock Awards; Employee Benefits Matters
    
    
    135.7.
    
    Fees and Expenses
    
    
    135.8.
    
    Directors and Officers Indemnification and Insurance
    
    
    135.9.
    
    Public Announcements
    
    
    135.10.
    
    Conveyance Taxes
    
    
    13
 i




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##### 



Page5.11.
    
    Restructuring of Merger
    
    
    13ARTICLE VI CONDITIONS PRECEDENT
    
    
    136.1.
    
    Conditions to Each Partys Obligation to Effect the Merger
    
    
    136.2.
    
    Additional Conditions to Obligations of Parent and Merger Sub
    
    
    136.3.
    
    Additional Conditions to Obligations of KeySpan
    
    
    13ARTICLE VII TERMINATION AND AMENDMENT
    
    
    137.1.
    
    Termination
    
    
    137.2.
    
    Effect of Termination
    
    
    137.3.
    
    Amendment
    
    
    137.4.
    
    Extension; Waiver
    
    
    13ARTICLE VIII GENERAL PROVISIONS
    
    
    138.1.
    
    Non-Survival of Representations, Warranties and Agreements
    
    
    138.2.
    
    Notices
    
    
    138.3.
    
    Interpretation
    
    
    138.4.
    
    Counterparts
    
    
    138.5.
    
    Entire Agreement; Third Party Beneficiaries
    
    
    138.6.
    
    Governing Law
    
    
    138.7.
    
    No Limitation on Other Representation
    
    
    138.8.
    
    Severability
    
    
    138.9.
    
    Assignment
    
    
    138.10.
    
    Submission to Jurisdiction; Waivers
    
    
    138.11.
    
    Enforcement
    
    
    138.12.
    
    Definitions
    
    
    138.13.
    
    Other Agreements
    
    
    13
 ii




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##### 



INDEX OF DEFINED TERMS
 Page(s)Acquisition Agreement
    
    
    32Additional KeySpan Consents
    
    
    31Agreement
    
    
    1Antitrust Law
    
    
    31Benefit Plans
    
    
    14Blue Sky Laws
    
    
    8Board of Directors
    
    
    46Business Day
    
    
    46Canceled Option
    
    
    34Certificate of Merger
    
    
    1Certificates
    
    
    3Circular
    
    
    27Closing
    
    
    1Closing Date
    
    
    1Code
    
    
    4Companies Act
    
    
    20Confidentiality Agreement
    
    
    30Constituent Corporations
    
    
    2DOJ
    
    
    30Effective Time
    
    
    1End Date
    
    
    41Environmental Laws
    
    
    17Environmental Permits
    
    
    17ERISA
    
    
    14Exchange Act
    
    
    8Exchange Agent
    
    
    3Exchange Fund
    
    
    3FCC
    
    
    8Federal Power Act
    
    
    8FERC
    
    
    10




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##### 



Page(s)Final Order
    
    
    38GAAP
    
    
    9Governmental Entity
    
    
    8HSR Act
    
    
    8Indemnified Parties
    
    
    36Joint Venture
    
    
    5KeySpan
    
    
    1KeySpan Benefit Plans
    
    
    14KeySpan Board Approval
    
    
    12KeySpan Certificates
    
    
    3KeySpan Common Stock
    
    
    2KeySpan Disclosure Schedule
    
    
    5KeySpan Employees
    
    
    35KeySpan Financial Advisor
    
    
    13KeySpan Financial Statements
    
    
    9KeySpan Intellectual Property
    
    
    17KeySpan Material Contracts
    
    
    17KeySpan Required Approvals
    
    
    8KeySpan SEC Reports
    
    
    9KeySpan Stockholders Meeting
    
    
    28Knowledge
    
    
    46Law
    
    
    8Liens
    
    
    7LSE
    
    
    19Material Adverse Effect
    
    
    46Materials of Environmental Concern
    
    
    17Merger
    
    
    1Merger Consideration
    
    
    2Merger Sub
    
    
    1Merger Sub Common Stock
    
    
    2NHPUC
    
    
    8NLRB
    
    
    15NYBCL
    
    
    1
 iv




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##### 



Page(s)NYPSC
    
    
    8Order
    
    
    8Other KeySpan Stock Awards
    
    
    34Parent
    
    
    1Parent Acquisition Transaction
    
    
    42Parent Board Approval
    
    
    21Parent Disclosure Schedule
    
    
    18Parent Required Approvals
    
    
    20Parent Shareholders Meeting
    
    
    29Parent Termination Fee
    
    
    42Permits
    
    
    11Person
    
    
    47Process Agent
    
    
    45Proxy Statement
    
    
    27PUHCA
    
    
    10Required KeySpan Vote
    
    
    12Required Parent Vote
    
    
    21Restraints
    
    
    38SEC
    
    
    9Securities Act
    
    
    9Significant Subsidiary
    
    
    47SOX
    
    
    9Subsidiary
    
    
    47Superior Proposal
    
    
    33Surviving Corporation
    
    
    2Surviving Corporation By-laws
    
    
    2Surviving Corporation Certificate of Incorporation
    
    
    2Takeover Proposal
    
    
    33Tax
    
    
    14Tax Return
    
    
    14Termination Fee
    
    
    41The Other Party
    
    
    47UK Listing Rules
    
    
    20
 v




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##### 



Page(s)UKLA
    
    
    20Violation
    
    
    8WARN Act
    
    
    16
 vi




---



##### 



Agreement Parent Merger Sub KeySpan
  Merger
     Effective Time of the Merger Certificate of Merger NYBCL Effective Time
 Closing Closing Closing Date
 Effects of the Merger




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##### 



Constituent
Corporations Surviving Corporation
 Certificate of Incorporation and By-Laws Surviving Corporation Certificate of
Incorporation Surviving Corporation By-laws
 Directors and Officers
  
 Effect on Capital Stock
 Merger Consideration KeySpan Common Stock Merger Consideration
 Conversion of Merger Sub Common Stock Merger Sub Common Stock
 2




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##### 



Cancellation of Certain KeySpan Capital Stock
 Surrender of Certificates
 Exchange Agent Exchange
Agent KeySpan Certificates Exchange Fund
 Exchange Procedures Certificates
 No Further Ownership Rights in KeySpan Common Stock
 3




---



##### 



Termination of Exchange Fund
 No Liability
 Lost, Stolen or Destroyed Certificates
 Withholding Code
 Transfers of Ownership
 4




---



##### 



Further Action
   Representations and Warranties of KeySpan KeySpan
Disclosure Schedule
 Organization, Standing and Power
 Joint Venture
 5




---



##### 



Subsidiaries
 Capital Structure
    6




---



##### 



Liens
    Authority; No Conflicts
   7




---



##### 



Violation Order Law
 Governmental Entity HSR Act Blue Sky
Laws Exchange Act NYPSC NHPUC Federal
Power Act FCC KeySpan Required Approvals
 Reports and Financial Statements
  8




---



##### 



Securities Act SEC KeySpan SEC Reports SOX
  principal executive officer principal financial officer extensions of credit
 KeySpan Financial Statements GAAP
  9




---



##### 



PUHCA FERC
   10




---



##### 



Compliance; Permits Permits
 Information Supplied
 11




---



##### 



Absence of Certain Changes or Events; Absence of Undisclosed Liabilities
   Board Approval KeySpan Board Approval
 Vote Required Required KeySpan Vote
 Takeover Statutes
 12




---



##### 



Brokers or Finders KeySpan
Financial Advisor
 Opinion of KeySpan Financial Advisor
 Taxes
 13




---



##### 



Tax Taxes Taxable Tax Return
 Benefit Plans ERISA Benefit Plans ERISA Affiliate KeySpan Benefit
Plans
  14




---



##### 



Labor Matters NLRB WARN Act
 15




---



##### 



Litigation
 Environmental Matters Environmental Laws
 16




---



##### 



Environmental Permits Materials of Environmental
Concern
 Intellectual Property KeySpan Intellectual
Property
 Insurance
 Interested Party Transactions
 Material Contracts
 KeySpan Material Contracts
 17




---



##### 



No Breach
 Foreign Corrupt Practices and International Trade Sanctions
 Representations and Warranties of Parent and Merger Sub Parent Disclosure Schedule
 Organization, Standing and Power
 Authority; No Violations
 18




---



##### 



LSE Parent Required
Approvals
 Compliance
 19




---



##### 



Litigation
 Information Supplied Companies Act UK Listing Rules UKLA
 Operations of Merger Sub
 Brokers or Finders
 20




---



##### 



Availability of Funds
 Board Approval Parent
Board Approval
 Vote Required Required Parent Vote
 Ownership of KeySpan Common Stock
   Covenants of KeySpan
 Ordinary Course of Business
 Dividends and Distributions, etc
 21




---



##### 



Issuance of Securities
 22




---



##### 



Charter Documents
 Acquisitions
 Capital Expenditures
 No Dispositions
 Indebtedness
 23




---



##### 



Compensation and Benefits
 Accounting
 Collective Bargaining Agreements
 Regulatory Status
 Insurance
 24




---



##### 



Certain Consents
 Taxes provided however
 Claims Settlement
 Waiver of Rights
 No Restrictions on Future Business Activities
 Actions to Impede Merger
 Agreement to do the Foregoing
 25




---



##### 



Covenants of Parent
 Conduct of Business of Merger Sub
 Conduct of Business of Parent
 Advice of Changes; Governmental Filings
 26




---



##### 



Transition Planning
 Control of Other Partys Business
   Preparation of Proxy Statement and Circular; Stockholders Meetings Proxy Statement
 Circular
 27




---



##### 



KeySpan Stockholders Meeting
 28




---



##### 



Parent Shareholders Meeting
 provided however provided further
 Corporate Governance
   Access to Information
 29




---



##### 



Confidentiality Agreement
 Reasonable Best Efforts
 DOJ
 30




---



##### 



provided however Antitrust Law
 31




---



##### 



No Solicitation by KeySpan Acquisition Agreement provided however bona fide
 32




---



##### 



Takeover Proposal Superior Proposal bona fide provided however
    33




---



##### 



KeySpan Stock Options and Other Stock Awards; Employee Benefits Matters Options Canceled
Option
 Other KeySpan Stock Awards Other KeySpan Stock Awards
 Employment Related Obligations; Employee Benefits
 Obligations of Parent; Comparability of Benefits
 34




---



##### 



KeySpan
Employees
 Pre-Existing Limitations; Deductible; Service Credit
 35




---



##### 



Fees and Expenses
 Directors and Officers Indemnification and Insurance Indemnified
Parties
  36




---



##### 



Public Announcements
 Conveyance Taxes
 Restructuring of Merger
 37




---



##### 



Conditions to Each Partys Obligation to Effect the Merger
 Required KeySpan Vote
 Required Parent Vote
 No Injunctions or Restraints; Illegality Restraints
 Approvals Final Order
 Additional Conditions to Obligations of Parent and Merger Sub
 Representations and Warranties
 38




---



##### 



provided
 Performance of Obligations of KeySpan
 Absence of Certain Changes or Events
 Certificate
 Additional Conditions to Obligations of KeySpan
 Representations and Warranties
 Performance of Obligations of Parent and Merger Sub
 Certificate
   Termination
  39




---



##### 



40




---



##### 



End Date
 Effect of Termination
 Termination Fee
   41




---



##### 



Parent Termination Fee Parent Acquisition Transaction
  Amendment
 Extension; Waiver
 42




---



##### 



Non-Survival of Representations, Warranties and Agreements
 Notices
 (a)
    
    if to Parent or Merger Sub to:National Grid USA
25 Research Drive
Westborough, Massachusetts 01582
Attention: Lawrence J. Reilly
Telecopy No.: (508) 389-2605with a copy to:Skadden, Arps, Slate, Meagher & Flom LLP
4 Times Square
New York, New York 10036
Attention: Sheldon S. Adler
Telecopy No.: (212) 735-2000(b)
    
    if to KeySpan to:KeySpan Corporation
One MetroTech Center
Brooklyn, New York 11201
Attention: John J. Bishar, Jr.
Telecopy No.: (718) 403-2809with a copy to:
 43




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##### 



Simpson Thacher & Bartlett LLP
425 Lexington Avenue
New York, New York 10017
Attention: Mario A. Ponce
Telecopy No.: (212) 455-2502
 Interpretation
 Counterparts
 Entire Agreement; Third Party Beneficiaries
  Governing Law
 No Limitation on Other Representation
 Severability
 44




---



##### 



Assignment
 Submission to Jurisdiction; Waivers Process Agent
 45




---



##### 



Enforcement
 Definitions
 Board of Directors
 Business Day
 Knowledge
 Material Adverse Effect provided however
 46




---



##### 



The Other Party
 Person
 Significant Subsidiary
 Subsidiary
 47




---



##### 



Other Agreements
  48




---



##### 



NATIONAL GRID PLCBy:
    /s/ Steven HollidayName:
    Steven HollidayTitle:
    Group DirectorNATIONAL GRID US8 INC.By:
    /s/ Michael E. JesanisName:
    Michael E. JesanisTitle:
    PresidentKEYSPAN CORPORATIONBy:
    /s/ Robert B. CatellName:
    Robert B. CatellTitle:
    Chairman and Chief Executive Officer 49