Holding(s) in Company

Northumbrian Water Group PLC
21 August 2007



TR-1(i): notification of major interests in shares

1. Identity of the issuer or the underlying issuer of existing shares to which
voting rights are attached(1): Northumbrian Water Group plc

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2. Reason for the notification                        
--------------------------------------------
An acquisition or disposal of voting rights                                Yes
--------------------------------------------                              -------
An acquisition or disposal of financial instruments which may result in      
the acquisition of shares already issued to which voting rights are       -------
attached
--------------------------------------------
An event changing the breakdown of voting rights                            
--------------------------------------------                              -------
Other (please specify):___________________________________________          
--------------------------------------------                              -------

3. Full name of person(s) subject to the         Ontario Teachers' Pension Plan
notification obligation(1):                      Board ("OTPPB")
-------------------------------                  --------------------
4. Full name of shareholder(s) (if different     As above.
from 3.)(1):                                     --------------------
-------------------------------
5. Date of the transaction (and date on which    17 August 2007
the threshold is crossed or reached if           --------------------
different)(1):
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6. Date on which issuer notified:                21 August 2007
-------------------------------                  --------------------
7. Threshold(s) that is/are
crossed or reached:                              26%
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8. Notified details:
-------------------------------                  --------------------

A: Voting rights attached to shares
Class/type   Situation previous to the     Resulting situation after the triggering
of shares    Triggering transaction (1)    triggering transaction (1)       
if possible
using the    Number of      Number of      Number of      Number of voting rights 
ISIN CODE    Shares         Voting Rights  shares                               
                                           Direct         Direct       Indirect   
                                                                         
Ordinary 10p 129,655,961    129,655,961    135,076,222    135,076,222             
GB0033029744

Percentage of voting rights
Direct       Indirect
26%

B: Financial Instruments
Resulting situation after the triggering transaction xii
Type of     Expiration Exercise/       Number of voting rights that may  % of
financial   date xiii  Conversion      be acquired if the instrument is  voting
instrument             Period/ Date    exercised/ converted.             rights
                       xiv


Total (A+B)
Number of voting rights                      % of voting rights
  135,076,222                                26.0%

9. Chain of controlled undertakings through which the voting rights and/or the
financial instruments are effectively held, if applicable xv:
The voting rights are held directly by OTPPB.

Proxy Voting:
10. Name of the proxy holder:                                              N/A
11. Number of voting rights proxy holder will cease to hold:               N/A
12. Date on which proxy holder will cease to hold voting rights:           N/A

13. Additional information:
14. Contact name:                  Kate Alsop, Assistant Company Secretary
15. Contact telephone number:      0191 301 6701




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