Rule 8.3 - O2 PLC

FORM 8.3

    DEALINGS BY PERSONS WITH INTERESTS IN SECURITIES REPRESENTING 1% OR MORE
              (Rule 8.3 of the City Code on Takeovers and Mergers)


1.   KEY INFORMATION

Name    of   person   dealing BARCLAYS PLC
(Note 1)
Company dealt in              O2 PLC
Class of relevant security    ORD GBP 0.001
to which the dealings being
disclosed relate (Note 2)
Date of dealing               16 DECEMBER 2005



2.   INTERESTS, SHORT POSITIONS AND RIGHTS TO SUBSCRIBE

(a)  Interests and short positions (following dealing) in the class of relevant
security dealt in (Note 3)

                                Long                  Short

                              Number       (%)       Number       (%)

(1) Relevant          270,769,588      (3.09%)       122,977  (0.00%)
securities
(2) Derivatives                 0      (0.00%)       325,000  (0.00%)
(other than options)
(3) Options and         1,001,400      (0.01%)     2,000,600  (0.02%)
agreements to
purchase/sell
Total                 271,770,988      (3.10%)     2,448,577  (0.03%)



(b)  Interests and short positions in relevant securities of the company, other
     than the class dealt in (Note 3)

Class of relevant          Long                     Short
security:

                   Number                                      Number
                                          (%)                                  (%)
(1)  Relevant
securities

(2)  Derivatives
(other than
options)

(3) Options and
agreements to
purchase/sell

Total


(c)  Rights to subscribe (Note 3)

Class of relevant security:   Details





3.   DEALINGS (Note 4)

(a)  Purchases and sales

Purchase/sale Number of Securities Price per unit
                                  (GBP)
Purchase      151,398              1.9700
Purchase      123,564              1.9653
Purchase      5,445                1.9600
Purchase      555                  Transfer
Purchase      303,174              1.9700
Purchase      17,306               1.9650
Sale          15,114               1.9654
Sale          45,736               1.9650
Sale          67,572               1.9650
Sale          151,398              1.9700
Sale          1,201                1.9676
Sale          222                  1.9676
Sale          597                  1.9676
Sale          88                   1.9676
Sale          460                  1.9651
Sale          822                  1.9651
Sale          1,000                1.9676
Sale          72                   1.9676
Sale          608                  1.9651
Sale          88                   1.9676



(b)  Derivatives transactions (other than options)

Product    Long/Short    Number of Securities  Price Per
name,      (Note 6)      (Note 7)              Unit (GBP)
e.g. CFD



(c)  Options transactions in respect of existing securities

(i)  Writing, selling, purchasing or varying

Product     Writing,     Number of    Exercise    Type,e.g.     Expiry   Option money
name,       selling,     securities   price       American,     date     paid/received
e.g. call   purchasing   to which                 European               per unit (note 5)
option      , varying    the option               etc.
            etc.         relates
                         (Note 7)


(ii) Exercising

Product name,  e.g. Number          of  Exercise  price   per
call option         securities          unit (Note 5)



(d)  Other dealings (including new securities) (Note 4)


Nature of transaction Details           Price per unit
(Note 8)                                (if applicable)
                                        (Note 5)


4.   OTHER INFORMATION

Agreements, arrangements or understandings relating to options or derivatives


Full details of any agreement, arrangement or understanding between the
person disclosing and any other person relating to the voting rights of
any relevant securities under any option referred to on this form or
relating to the voting rights or future acquisition or disposal of any
relevant securities to which any derivative referred to on this form is
referenced.  If none, this should be stated.





Is a Supplemental Form 8 attached? (Note 9)                 NO


Date of disclosure                         19 DECEMBER 2005
Contact name                               BARCLAYS CORPORATE SECRETARIAT
Telephone number                           020 7116 2913
If  a  connected EFM, name of
offeree/offeror with which connected
If a connected EFM, state nature of
connection (Note 10)


Notes

The Notes on Form 8.3 can be viewed on the Takeover Panel's website at
www.thetakeoverpanel.org.uk