SCHEDULE 13G

Amendment No. 5
COLT Telecom Group Plc
Ordinary Shares
Cusip # G22944121

Cusip # G22944121
Item 1:	Reporting Person - FMR Corp.
Item 4:	Commonwealth of Massachusetts
Item 5:	365,845,160
Item 6:	0
Item 7:	365,845,160
Item 8:	0
Item 9:	365,845,160
Item 11:	52.21%
Item 12:	    HC

Cusip # G22944121
Item 1:	Reporting Person - Edward C. Johnson 3d
Item 4:	United States of America
Item 5:	0
Item 6:	0
Item 7:	365,845,160
Item 8:	0
Item 9:	365,845,160
Item 11:	52.21%
Item 12:	IN

Cusip # G22944121
Item 1:	Reporting Person - Abigail P. Johnson
Item 4:	United States of America
Item 5:	0
Item 6:	0
Item 7:	365,845,160
Item 8:	0
Item 9:	365,845,160
Item 11:	52.21%
Item 12:	    IN


SCHEDULE 13G - TO BE INCLUDED IN STATEMENTS
FILED PURSUANT TO RULE 13d-1(b) or 13d-2(b)


Item 1(a).	Name of Issuer:

		COLT Telecom Group Plc

Item 1(b).	Name of Issuer's Principal Executive Offices:

		15 Marylebone Road
		London, NW15JD
		United Kingdom

Item 2(a).	Name of Person Filing:

		FMR Corp.

Item 2(b).	Address or Principal Business Office or, if None,
Residence:

		82 Devonshire Street, Boston, Massachusetts  02109

Item 2(c).	Citizenship:

		Not applicable

Item 2(d).	Title of Class of Securities:

		Ordinary Shares

Item 2(e).	CUSIP Number:

		G22944121

Item 3.	This statement is filed pursuant to Rule 13d-1(b) or 13d-
2(b) and the person filing, FMR Corp., is a parent holding company in
accordance with Section 240.13d-1(b)(ii)(G).  (Note:  See Item 7).

Item 4.	Ownership

	(a)	Amount Beneficially Owned:	365,845,160

	(b)	Percent of Class:	52.21%

	(c)	Number of shares as to which such person has:

	(i)	sole power to vote or to direct the vote:	365,845,160

	(ii)	shared power to vote or to direct the vote:	0

	(iii)	sole power to dispose or to direct the disposition of:
	365,845,160

	(iv)	shared power to dispose or to direct the disposition of:
	0



Item 5.	Ownership of Five Percent or Less of a Class.

	Not applicable.

Item 6.	Ownership of More than Five Percent on Behalf of Another
Person.

			Various persons beneficially own and have the right
to receive or the power to direct the receipt of dividends from, or the
proceeds from the sale of, the ordinary shares of COLT Telecom Group
Plc.
			The interest of Colt, Inc. in the ordinary shares of
COLT Telecom Group Plc amounted to 156,742,080 shares or 22.37% of the
total ordinary shares deemed to be outstanding at December 31, 2000.
			The interest of Fidelity Investors Limited
Partnership in the ordinary shares of COLT Telecom Group Plc amounted
to 151,049,560 shares or 21.55% of the total ordinary shares deemed to
be outstanding at December 31, 2000.

Item 7.	Identification and Classification of the Subsidiary Which
Acquired the Security Being Reported on By the Parent Holding Company.

	See attached Exhibit(s) A, B, and C.

Item 8.	Identification and Classification of Members of the Group.

	Not Applicable. See attached Exhibit A.

Item 9.	Notice of Dissolution of Group.

	Not applicable.

Item 10.	Certification.

	Not applicable.

Signature

	After reasonable inquiry and to the best of my knowledge and
belief, I certify that the information set forth in this Schedule 13G
in connection with FMR Corp.'s beneficial ownership of the Ordinary
Shares of COLT Telecom Group Plc at December 31, 2000 is true, complete
and correct.

	February 14, 2000
Date


	/s/Eric D. Roiter
Signature


	Eric D. Roiter
	Duly authorized under Power of Attorney
	dated December 30, 1997, by and on behalf
	of FMR Corp. and its direct and indirect
	subsidiaries


				Exhibit A
SCHEDULE 13G - TO BE INCLUDED IN STATEMENTS
FILED PURSUANT TO RULE 13d-1(b) or 13d-2(b)

	Colt, Inc. ("COLT"), 82 Devonshire Street, Boston, Massachusetts
02109, an indirect wholly-owned subsidiary of FMR Corp., is the
beneficial owner of 156,742,080 shares or 22.37% of the ordinary shares
deemed to be outstanding of COLT Telecom Group Plc ("the Company").

	Edward C. Johnson 3d, Chairman and Chief Executive Officer of FMR
Corp., and FMR Corp., each may be deemed to have sole power to vote or
direct the vote and to dispose of the 156,742,080 ordinary shares owned
by COLT.

	Strategic Advisers, Inc., 82 Devonshire Street, Boston, MA 02109,
a wholly-owned subsidiary of FMR Corp. and an investment adviser
registered under Section 203 of the Investment Advisers Act of 1940,
provides investment advisory services to individuals.  Strategic
Advisers, Inc. has sole voting and dispositive power over 29,913,045
shares or 4.27% of the ordinary shares deemed to be outstanding at
December 31, 2000, beneficially owned through Strategic Advisers, Inc.

	Fidelity Investors Limited Partnership ("FILP"), 82 Devonshire
Street, Boston, Massachusetts 02109, a Delaware limited partnership, is
the beneficial owner of 151,049,560 shares or 21.55% of the ordinary
shares deemed to be outstanding at December 31, 2000 of the Company.
Fidelity Investors Management, LLC ("FIML"), a Delaware limited
liability company, is the general partner and investment manager of
FILP, and is an investment manager registered under Section 203 of the
Investment Advisers Act of 1940.  The members of FIML and the limited
partners of FILP are certain shareholders and employees of FMR Corp.

	Members of the Edward C. Johnson 3d family are the predominant
owners of Class B shares of common stock of FMR Corp., representing
approximately 49% of the voting power of FMR Corp.  Mr. Johnson 3d owns
12.0% and Abigail Johnson owns 24.5% of the aggregate outstanding
voting stock of FMR Corp.  Mr. Johnson 3d is Chairman of FMR Corp. and
Abigail P. Johnson is a Director of FMR Corp.  The Johnson family group
and all other Class B shareholders have entered into a shareholders'
voting agreement under which all Class B shares will be voted in
accordance with the majority vote of Class B shares.  Accordingly,
through their ownership of voting common stock and the execution of the
shareholders' voting agreement, members of the Johnson family may be
deemed, under the Investment Company Act of 1940, to form a controlling
group with respect to FMR Corp.

	Fidelity International Limited, Pembroke Hall, 42 Crowlane,
Hamilton, Bermuda, and various foreign-based subsidiaries provide
investment advisory and management services to a number of non-U.S.
investment companies and certain institutional investors.  Fidelity
International Limited is the beneficial owner of 28,140,475 ordinary
shares or 4.02% of the ordinary shares deemed to be outstanding at
December 31, 2000 of the Company.  Additional information with respect
to the beneficial ownership of Fidelity International Limited is shown
on Exhibit B, page 9.


Exhibit B
SCHEDULE 13G - TO BE INCLUDED IN STATEMENTS
FILED PURSUANT TO RULE 13d-1(b) or 13d-2(b)

	This Exhibit has been prepared  to identify Fidelity
International Limited (FIL), Pembroke Hall, 42 Crow Lane, Hamilton,
Bermuda, a Bermudan joint stock company incorporated for an unlimited
duration by private act of the Bermuda Legislature and an investment
adviser to various investment companies and certain institutional
investors, as a beneficial owner of the 28,140,475 ordinary shares or
4.02% of the ordinary shares deemed to be outstanding at December 31,
2000 of the Company.

	Prior to June 30, 1980, FIL was a majority-owned subsidiary of
Fidelity Management & Research Company (Fidelity), a wholly-owned
subsidiary of FMR Corp.  On that date, the shares of FIL held by
Fidelity were distributed, as a dividend,  to the shareholders of FMR
Corp.  FIL currently operates as an entity independent of FMR Corp. and
Fidelity.  The International Funds and FIL's other clients, with the
exception of Fidelity and an affiliated company of Fidelity, are non-
U.S. entities.

	A partnership controlled by Edward C. Johnson 3d and members of
his family owns shares of FIL voting stock with the right to cast
approximately 39.89% of the total votes which may be cast by all
holders of FIL voting stock.  Mr. Johnson 3d is Chairman of FMR Corp.
and FIL.  FMR Corp. and FIL are separate and independent corporate
entities, and their Boards of Directors are generally composed of
different individuals.  Other than when one serves as a sub adviser to
the other, their investment decisions are made independently, and their
clients are generally different organizations.

	FMR Corp. and FIL are of the view that they are not acting as a
"group" for purposes of Section 13(d) under the Securities Exchange Act
of 1934 (the "1934" Act) and that they are not otherwise required to
attribute to each other the "beneficial ownership" of securities
"beneficially owned" by the other corporation within the meaning of
Rule 13d-3 promulgated under the 1934 Act.  Therefore, they are of the
view that the shares held by the other corporation need not be
aggregated for purposes of Section 13(d). However, FMR Corp. is making
this filing on a voluntary basis as if all of the shares are
beneficially owned by FMR Corp. and FIL on a joint basis.

	FIL does not have a present plan or proposal which relates to or
would result in (i) an extraordinary corporate transaction, such as a
merger, reorganization, liquidation, or sale or transfer of a material
amount of assets involving the Company or any of its subsidiaries, (ii)
any change in the Company's present Board of Directors or management,
(iii) any material changes in the Company's present capitalization or
dividend policy or any other material change in the Company's business
or corporate structure, (iv) any change in the Company's charter or by-
laws, or (v) the Company's common stock becoming eligible for
termination of its registration pursuant to Section 12(g)(4) of the
1934 Act.







 .


Exhibit C
SCHEDULE 13G - TO BE INCLUDED IN STATEMENTS
FILED PURSUANT TO RULE 13d-1(b) or 13d-2(b)
RULE 13d-1(f)(1)  AGREEMENT

	The undersigned persons, on February 14, 2001, agree and consent
to the joint filing on their behalf of this Schedule 13G in connection
with their beneficial ownership of the Ordinary Shares of COLT Telecom
Group Plc at December 31, 2000.

FMR Corp.

By   /s/Eric D. Roiter
	Eric D. Roiter
	Duly authorized under Power of Attorney
	dated December 30, 1997, by and on behalf
	of FMR Corp. and its direct and indirect
	subsidiaries

Edward C. Johnson 3d

By   /s/Eric D. Roiter
	Eric D. Roiter
	Duly authorized under Power of Attorney
	dated December 30, 1997, by and on behalf
	of Edward C. Johnson 3d

Abigail P. Johnson

By   /s/Eric D. Roiter
	Eric D. Roiter
	Duly authorized under Power of Attorney
	dated December 30, 1997, by and on behalf
	of Abigail P. Johnson

Fidelity Management & Research Company

By   /s/Eric D. Roiter
	Eric D. Roiter
	Senior V.P. and General Counsel