SCHEDULE 13G 
 
Amendment No. 2 
Colt Telecom Group plc 
Ordinary Shares 
Cusip # 19699E220 
 
 
Cusip # 19699E220 
Item 1:	Reporting Person - FMR Corp. - (Tax ID:  04-2507163) 
Item 4:	Commonwealth of Massachusetts 
Item 5:	342,844,728  ordinary shares (4,637,676 shares issuable upon  
conversion of the Junior  
	Subordinated Debentures) 
Item 6:	None 
Item 7:	342,844,728  ordinary shares (4,637,676 shares issuable upon  
conversion of the Junior  
	Subordinated Debentures) 
Item 8:	None 
Item 9:	342,844,728  ordinary shares (4,637,676 shares issuable upon  
conversion of the Junior  
	Subordinated Debentures) 
Item 11:	55.39% 
Item 12:	HC  
 
 
 
 
Cusip # 19699E220 
Item 1:	Reporting Person - Edward C. Johnson 3d  
Item 4:	United States of America 
Item 5:	None 
Item 6:	None 
Item 7:	342,844,728 ordinary shares (4,637,676 shares issuable upon conversion  
of the Junior  
	Subordinated Debentures) 
Item 8:	None 
Item 9:	342,844,728 ordinary shares (4,637,676 shares issuable upon conversion  
of the Junior  
	Subordinated Debentures) 
Item 11:	55.39% 
Item 12:	IN  
 
 
 
Cusip # 19699E220 
Item 1:	Reporting Person - Abigail P. Johnson  
Item 4:	United States of America 
Item 5:	None 
Item 6:	None 
Item 7:	342,844,728 ordinary shares (4,637,676 shares issuable upon conversion  
of the Junior  
	Subordinated Debentures) 
Item 8:	None 
Item 9:	342,844,728 ordinary shares (4,637,676 shares issuable upon conversion  
of the Junior  
	Subordinated Debentures) 
Item 11:	55.39% 
Item 12:	IN  
 
 
 
 
 
 
Item 1(a).	Name of Issuer: 
 
		Colt Telecom Group plc 
 
Item 1(b).	Name of Issuer's Principal Executive Offices: 
 
		Bishopsgate Court, 4 Norton Folgate 
		London, E1 6DQ  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:   
 
		19699E220 
 
Item 3.	Not applicable 
 
Item 4.	Ownership 
 
	(a)	Amount Beneficially Owned: 
	342,844,728 
 
	(b)	Percent of Class: 
	55.39% 
 
	(c)	Number of shares as to which such person has:   
 
	(i)	sole power to vote or to direct the vote: 
	342,844,728 
 
	(ii)	shared power to vote or to direct the vote: 
	None 
 
	(iii)	sole power to dispose or to direct the disposition of: 
	342,844,728 
 
	(iv)	shared power to dispose or to direct the disposition of: 
	None 
 
 
 
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 covered by this Schedule 13G. 
  		The interest of  Colt Inc. in the ordinary shares of Colt  
Telecom Group plc amounted to 162,070,111 shares or 26.18% of  
the total ordinary shares deemed to be outstanding at December  
31, 1998.  The number of ordinary shares also includes  
5,181,000 shares that are held by a trust over which Colt Inc.  
has voting control, and the power to approve payments made from  
the trust, (which must be made pursuant to an employee benefit  
plan), and in which Colt Inc. has a residual ownership  
interest. Colt Inc. also holds an option to acquire, at a  
nominal price, a special share of Colt Telecom Group plc which,  
during a period ending on or, in certain cases, before December  
31, 2001, will confer on the holder thereof the right, if a  
person other than Colt Inc., FMR Corp., Fidelity Investors  
Limited Partnership, Fidelity International Limited, or their  
affiliates acquires more than 30% of the outstanding shares of  
Colt Telecom Group plc to cast a majority of the votes cast at  
any of its shareholders meetings. 
	 	The interest of  Fidelity Investors Limited Partnership  
in the ordinary shares of Colt Telecom Group plc amounted to  
143,194,691 shares or 23.14% of the total ordinary shares  
deemed to be outstanding at December 31, 1998.   
			The interest of  Fidelity International Limited in the  
ordinary shares of Colt Telecom Group plc amounted to  
32,237,676 shares or 5.21% of the total ordinary shares deemed  
to be outstanding at December 31, 1998.  The number of ordinary  
shares beneficially owned by Fidelity International Limited at  
December 31, 1998 included 4,637,676 shares of ordinary shares  
resulting from the assumed conversion of the Junior  
Subordinated Debentures. 
 
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, and B. 
 
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, 1998 is true, complete and correct.  
 
 
 
	February 26, 1999	 
Date 
 
 
 
	/s/Frank V. Knox 
Signature 
 
 
 
	Frank V. Knox 
Duly authorized under Power of  
Attorney 
dated February 24, 1999, by Eric. D. Roiter, by  
and on behalf of FMR Corp. and its direct and  
indirect subsidiaries 
 
 
 
  
	Colt Inc. ("COLT"), 82 Devonshire Street, Boston, Massachusetts 02109, an  
indirect wholly-owned subsidiary of FMR Corp., is the beneficial owner of  
162,070,111 ordinary shares or 26.18% 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 162,070,111 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 the 5,342,250 ordinary shares.  As such, FMR  
Corp.'s beneficial ownership includes 5,342,250 shares, or 0.86%, of the total  
ordinary shares deemed to be outstanding at December 31, 1998, beneficially  
owned through Strategic Advisers, Inc. 
 
	Fidelity Investors Limited Partnership ("FILP"), 82 Devonshire Street,  
Boston, Massachusetts 02109, a Delaware limited partnership, the general  
partner of which is owned by, and the limited partners of which are, certain  
shareholders and employees of FMR Corp., including Edward C. Johnson 3d, is  
the beneficial owner of 143,194,691 ordinary shares or 23.14% of the total  
ordinary shares deemed to be outstanding at December 31, 1998.  
 
	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 also the  
beneficial owner of 32,237,676 ordinary shares or 5.21% of the ordinary shares  
deemed to be outstanding of the Company.  Additional information with respect  
to the beneficial ownership of Fidelity International Limited is shown on  
Exhibit B, page 10. 
 
 
 
 
	This Exhibit has been prepared  to identify Fidelity International  
Limited, Pembroke Hall, 42 Crow Lane, Hamilton, Bermuda, a Bermudian joint  
stock company incorporated for an unlimited duration by private act of the  
Bermuda Legislature (FIL) and an investment adviser to various investment  
companies (the "International Funds") and certain institutional investors, as  
the beneficial owner of 32,237,676 ordinary shares or 5.21% of the ordinary  
shares outstanding of Colt Telecom Group plc, which shares are held for the  
account of FIL and not the international funds.  The number of ordinary shares  
beneficially  owned by Fidelity International Limited at December 31, 1998  
included 4,637,676 ordinary shares resulting from the assumed conversion of  
the Junior Subordinated Debentures. 
 
	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  
47.22% 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. 
 
	   
 
 
	The undersigned persons, on February 26, 1999, 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, 1998. 
 
	FMR Corp. 
	By	/s/Frank V. Knox 
Frank V. Knox 
Duly authorized under Power of  
Attorney by Eric D. Roiter  
dated  February 24, 1999, by  
and on behalf of FMR Corp. and  
its direct and indirect  
subsidiaries 
 
	Edward C. Johnson 3d 
	By	/s/Frank V. Knox 
Frank V. Knox 
Duly authorized under Power of  
Attorney by Eric D. Roiter  
dated  February 24, 1999, by  
and on behalf of Edward C.  
Johnson 3d 
 
	Abigail P. Johnson 
 
	By	/s/Frank V. Knox 
Frank V. Knox 
Duly authorized under Power of  
Attorney by Eric D. Roiter  
dated  February 24, 1999, by  
and on behalf of Abigail P.  
Johnson 
 
	Colt Inc. 
	By	/s/Lena G. Goldberg 
Lena G. Goldberg 
Vice President 
 
	Fidelity Investors Limited Partnership 
	By:  Fidelity Investors Management, LLC 
	its General Partner 
	By	/s/Jay Freedman 
Jay Freedman 
Secretary 
 
 
 
	Fidelity International Limited  
	By	/s/Frank V. Knox 
Frank V. Knox 
Duly authorized under Power of  
Attorney by Eric D. Roiter  
dated  February 24, 1999, by  
and on behalf of Fidelity  
International Limited and its  
direct and indirect  
subsidiaries