UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                            SCHEDULE 14A INFORMATION
                                 (Rule 14a-101)

                  Proxy Statement Pursuant to Section 14(a) of
            the Securities and Exchange Act of 1934 (Amendment No. )

Filed by the Registrant  [X]
Filed by a Party other than the Registrant  [ ]

Check the appropriate box:
[ ]     Preliminary Proxy Statement
[ ]     Confidential, For Use of the Commission Only (as permitted by Rule
        14a-6(e)(2))
[ ]     Definitive Proxy Statement
[ ]     Definitive Additional Materials
[X]     Soliciting Material Pursuant to Section 240.14a-12

                               KeySpan Corporation
                               -------------------
                (Name of Registrant as Specified in Its Charter)

                                      (N/A)
                                      -----
    (Name of Person(s) Filing Proxy Statement, if Other Than the Registrant)

Payment of Filing Fee (Check the appropriate box):
[X]  No fee required.
[ ]  Fee computed on table below per Exchange Act Rules 14a-6(i)(1) and 0-11.

(1)  Title of each class of securities to which transaction applies:
     N/A______________________________________________________________
(2)  Aggregate number of securities to which transaction applies:
     N/A______________________________________________________________
(3)  Per unit price or other underlying value of transaction  computed  pursuant
     to Exchange  Act Rule 0-11 (set forth the amount on which the filing fee is
     calculated and state how it was determined):
     N/A______________________________________________________________
(4)  Proposed maximum aggregate value of transaction:
     N/A______________________________________________________________
(5)  Total fee paid:
     N/A______________________________________________________________

[ ]  Fee paid previously with preliminary materials.
[ ]  Check box if any part of the fee is offset as provided by Exchange Act Rule
     0-11(a)(2)  and identify the filing for which the  offsetting  fee was paid
     previously.  Identify the previous filing registration statement number, or
     the Form or Schedule and date of its filing.





(1)  Amount Previously Paid:
     N/A______________________________________________________________
(2)  Form, Schedule or Registration Statement No.:
     N/A______________________________________________________________
(3)  Filing Party:
     N/A______________________________________________________________
(4)  Date Filed:
     N/A______________________________________________________________









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The following  letter is being  distributed to all active and retired  employees
that participate in KeySpan's 401(k) plans:

March 2006

          Important Information Regarding the KeySpan Common Stock Fund
                           in Your KeySpan 401(k) Plan


As you may know, KeySpan has announced that it has entered into an Agreement and
Plan of Merger with  National  Grid.  With the  impending  transaction,  we, the
KeySpan  Investment  Review Committee as fiduciaries for the KeySpan 401(k) Plan
("the  Plan"),  expect there will be no change to any  provisions of the Plan or
the way in which the Plan is managed for the  immediate  future.  As a result of
this  announcement,  you may have some  questions  regarding the KeySpan  Common
Stock Fund in the Plan.  The purpose of this letter is to address  some of those
questions.

Q. Will the KeySpan Common Stock Fund remain an investment option in the Plan?

A. Until the transaction is consummated,  KeySpan  anticipates  that the KeySpan
Common Stock Fund will remain an investment  option in the Plan.  Therefore,  no
action needs to be taken at this time if you'd like to continue to invest in the
KeySpan  Common Stock Fund.  Once the  transaction is  consummated,  the KeySpan
Common Stock Fund will be eliminated as an option in the Plan.

Q. What will happen to my investment  in the KeySpan  Common Stock Fund once the
merger transaction is consummated?

A. At the time of merger,  National Grid will purchase all outstanding shares of
KeySpan  Common Stock for $42 per share and any holdings you have in the KeySpan
Common Stock Fund will be converted to cash.  At that time,  you will be able to
allocate  the cash  proceeds  to  another  investment  option  within the Plan's
then-current fund lineup.

Q. Can I still allocate contributions to the KeySpan Common Stock Fund?

A. Yes.  We  anticipate  that until the  transaction  is  consummated,  you will
continue to be able to allocate all or a portion of your  Pre-Tax  Contributions
and/or your Employer  Matching  Contributions  to the KeySpan Common Stock Fund.
Please  note  that  continued  investment  in any fund  offered  under the Plan,
including  the KeySpan  Common Stock Fund,  is subject to the  discretion of the
KeySpan Investment Review Committee.

Q. Will I still  receive a discount on the  purchase of KeySpan  Common Stock in
the Plan?

A. Yes.  If you are  currently  eligible,  you will  continue  to  receive a 10%
discount on the  purchase of KeySpan  Common  Stock in the KeySpan  Common Stock
Fund.

Q. Will I still receive  dividends on KeySpan Common Stock in the KeySpan Common
Stock Fund?

A. Yes. As long as KeySpan's Board of Directors  continues to declare dividends,
you will continue to receive  dividends on any KeySpan Common Stock holdings you
have in the Plan until the transaction is consummated.

Q. Can I exchange  my  holdings  in the  KeySpan  Common  Stock Fund to purchase
shares of National Grid?

A. No. Currently National Grid shares are not an investment option in the Plan.


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Please be assured  that we are  committed  to  keeping  you  informed  about any
changes to the Plan and will  continue  to  communicate  with you as KeySpan and
National  Grid work  toward the  consummation  of the  transaction.  If you have
questions  about this upcoming  change or any other aspect of your Plan,  please
contact  Vanguard(R)  Participant  Services at 800-523-1188 or the KeySpan Stock
Plans Hotline at 718-403-3131.

Sincerely,

The KeySpan Investment Review Committee

/s/Gerald Luterman,                             /s/Lenore Puleo,
   Executive Vice President                        Executive Vice President
   & Chief Financial Officer                       Shared Services


/s/Michael Taunton,                             /s/Justin Orlando
   Senior Vice President, Treasurer                Vice President
   & Chief Risk Officer                            Human Resources


/s/Richard A. Rapp, Jr.,
   Vice President
   Energy Transactions



Additional Information and Where to Find It
- -------------------------------------------

KeySpan  intends to file with the Securities and Exchange  Commission  ("SEC") a
proxy  statement and other  relevant  documents in connection  with the proposed
transaction between KeySpan and National Grid. Investors and security holders of
KeySpan are advised to read the proxy  statement  and other  relevant  documents
when they become available, as they will contain important information about the
transaction.  Investors and security holders may obtain a free copy of the proxy
statement  and other  documents  filed by KeySpan with the SEC, when they become
available, at the SEC's web site at www.sec.gov.

KeySpan and its directors,  executive officers,  other members of its management
and employees may be deemed to be  participants  in the  solicitation of proxies
from  its  security  holders  in  connection  with  the  proposed   transaction.
Information   concerning  the  interests  of  KeySpan's   participants   in  the
solicitation  is set forth in KeySpan's  most recent proxy  statement and Annual
Report on Form 10-K (filed with the Securities and Exchange  Commission on March
30, 2005,  and March 2, 2006,  respectively)  and will be set forth in the proxy
statement relating to the merger when it becomes available.



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Additional Information and Where to Find It
- -------------------------------------------

KeySpan intends to file with the Securities and Exchange  Commission (the "SEC")
a proxy  statement and other relevant  documents in connection with the proposed
acquisition  of KeySpan by National  Grid.  Investors  and  security  holders of
KeySpan are advised to read the proxy  statement  and other  relevant  documents
when they become available, as they will contain important information about the
transaction.  Investors and security holders may obtain a free copy of the proxy
statement  and other  documents  filed by KeySpan with the SEC, when they become
available, at the SEC's web site at http:/www.sec.gov.

KeySpan  and  its  directors,  executive  officers  and  other  members  of  its
management and employees may be deemed to be participants in the solicitation of
proxies from its security  holders in connection with the proposed  acquisition.
Information   concerning  the  interests  of  KeySpan's   participants   in  the
solicitation  is set forth in KeySpan's  most recent proxy  statement and Annual
Report on Form 10-K (filed with the SEC on March 30, 2005 and February 28, 2006,
respectively)  and will be set  forth in the  proxy  statement  relating  to the
acquisition when it becomes available.




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