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, 2005


                             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)







                        BLOCKLISTING SIX MONTHLY RETURN

Information provided on this form must be typed or printed electronically.


To: The FSA

Date: 16 December 2005


1. Name of applicant:

COLT Telecom Group plc

2. Name of scheme

COLT Telecom Group Warrants

3. Period of return:

From   19.06.05         To   16.12.05

4. Balance under scheme from previous return:

606,999

5. The amount by which the block scheme has been increased, if the scheme has
been increased since the date of the last return

NIL

6. Number of securities issued/allotted under scheme during period:

NIL

7 Balance under scheme not yet issued/allotted at end of period

606,999

8. Number and class of securities originally listed and the date of admission

9,796,800 18.06.1997

9. Total number of securities in issue at the end of the period

1,512,636,057

Name of contact                 Michaella Henderson

Address of contact              Beaufort House, 15 St Botolph Street, London,
                                EC3A 7QN

Telephone number of contact     0207 947 1064

Signed by Caroline Griffin Pain, Company Secretary for and on behalf of COLT
Telecom Group plc







                                     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: 16 December 2005                         COLT Telecom Group plc


                                               By: ___Caroline Griffin Pain___

                                               Caroline Griffin Pain
                                               Company Secretary