EXHIBIT 12.1

I, Steven P. Akin, certify that:

|1. | I have reviewed this annual report on Form 20-F of COLT Telecom Group plc;
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|2. | Based on my knowledge, this report does not contain any untrue statement of a
          material fact or omit to state a material fact necessary to make the statements
          made, in light of the circumstances under which such statements were made, not
          misleading with respect to the period covered by this report;
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|3. | Based on my knowledge, the financial statements, and other financial information
          included in this report, fairly present in all material respects the financial
          condition, results of operations and cash flows of the company as of, and for,
          the periods presented in this report;
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|4. | The companys other certifying officer(s) and I are responsible for
          establishing and maintaining disclosure controls and procedures (as defined in
          Exchange Act Rules 13a-15(e) and 15d-15(e)) for the company and have:
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| | (a) |  | Designed
such disclosure controls and procedures, or caused such disclosure
                    controls and procedures to be designed under our supervision, to
ensure that                     material information relating to the company, including
its consolidated                     subsidiaries, is made known to us by others within
those entities, particularly                     during the period in which this report
is being prepared;
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| | (b) |  | Evaluated
the effectiveness of the companys disclosure controls and
                    procedures and presented in this report our conclusions about the
effectiveness                     of the disclosure controls and procedures, as of the
end of the period covered                     by this report based on such evaluation;
and
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| | (c) |  | Disclosed
in this report any change in the companys internal control over
                    financial reporting that occurred during the period covered by the
annual report                     that has materially affected, or is reasonably likely
to materially affect, the                     companys internal control over
financial reporting; and
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|5. | The companys other certifying officer(s) and I have disclosed, based on
          our most recent evaluation of internal control over financial reporting, to the
          companys auditors and the audit committee of the companys board of
          directors (or persons performing the equivalent functions):
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| | (a) |  | All
significant deficiencies and material weaknesses in the design or operation
                    of internal control over financial reporting which are reasonably
likely to                     adversely affect the companys ability to record,
process, summarize and                     report financial information; and
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| | (b) |  | Any
fraud, whether or not material, that involves management or other employees
                    who have a significant role in the companys internal control
over                     financial reporting.
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/s/ Steven P. AkinSteven
P. Akin President and Chief
Executive Officer

Dated as of 30 April 2004