FORM 6-K

                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549


                            Report of Foreign Issuer


                      Pursuant to Rule 13a-16 or 15d-16 of
                       the Securities Exchange Act of 1934


                         For the month of December, 2004


                             COLT TELECOM GROUP plc
                 (Translation of Registrant's Name into English)


                                 Beaufort House
                              15 St. Botolph Street
                                     London
                                    EC3A 7QN
                                     England

                        _________________________________
                    (Address of Principal Executive Offices)



(Indicate by check mark whether the Registrant files or will file annual
reports under cover of Form 20-F or Form 40-F.)


                        Form 20-F..X...    Form 40-F.....



(Indicate by check mark whether the Registrant by furnishing the information
contained in this Form is also thereby furnishing the information to the
Commission pursuant to Rule 12g3-2(b) under the Securities Exchange Act of 1934)


                              Yes .....    No ..X...


(If "Yes" is marked, indicate below the file number assigned to the Registrant
in connection with Rule 12g3-2(b): 82- ________)



This Form 6-K shall be deemed to be incorporated by reference in the
Registrant's Registration Statement on Form F-3 (Reg. No.333-05972), in the
Registrant's Registration Statement on Form S-8 (Reg. No.333-8362)






                                   SCHEDULE 5
                        BLOCK LISTING SIX MONTHLY RETURN


To: Listing Applications
    UK Listing Authority
    Financial Services Authority
    25, The North Colonnade
    Canary Wharf
    London, E14 5HS


               Please ensure the entries on this return are typed

1.  Name of company COLT Telecom Group plc

2.  Name of scheme COLT Telecom Group Warrants

3.  Period of return: From 19.06.2004 to 18.12.2004

4.  Number and class of share(s) (amount of stock/debt security)       606,999
    not issued under scheme

5.  Number of shares issued/allotted under scheme during period:             0

6.  Balance under scheme not yet issued/allotted at end of             606,999
    period

7.  Number and class of share(s) (amount of stock/debt securities)   9,796,800
    originally listed and the date of admission;                    18.06.1997

Please confirm total number of shares in issue at the end of the period in order
for us to update our records 1,511,048,701

Contact for queries:                     Address: Beaufort House
Name: Adrian Goodenough                  15 St. Botolph Street
Telephone: 020 7947 1677                 London EC3A 7QN

Person making return
Name: Adrian Goodenough
Position:
Signature:






                                     SIGNATURES


Pursuant to the requirements of the Securities Exchange Act of 1934, the
registrant has duly caused this Current Report on Form-6K to be signed on its
behalf by undersigned, thereunto duly authorized.



Date: 21 December 2004                               COLT Telecom Group plc


                                                     By: ___Jane Forrest___

                                                     Jane Forrest
                                                     Company Secretary