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EXHIBIT 31.1

I, Michael Parton, certify that:



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| | 1. | I have reviewed this Form 10-Q of Marconi
    Corporation 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 registrant as of,
    and for, the periods presented in this report;                                                    
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| | 4. | The registrant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)) and internal control over
    financial reporting (as defined in Exchange Act
    Rules 13a-15(f) and 15d-15(f)) for the registrant 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 registrant, 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) | Designed such internal control over financial
    reporting, or caused such internal control over financial
    reporting to be designed under our supervision, to provide
    reasonable assurance regarding the reliability of financial
    reporting and the preparation of financial statements for
    external purposes in accordance with generally accepted
    accounting principles;       
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| | (c) | Evaluated the effectiveness of the
    registrant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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| | (d) | Disclosed in this report any change in the
    registrants internal control over financial reporting that
    occurred during the registrants most recent fiscal quarter
    that has materially affected, or is reasonably likely to
    materially affect, the registrants internal control over
    financial reporting; and                                                                    



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| | 5. | The registrants other certifying officer(s)
    and I have disclosed, based on our most recent evaluation of
    internal control over financial reporting, to the
    registrants auditors and the audit committee of the
    registrant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 registrant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
    registrants internal control over financial reporting.                                                                                                       



| |                        
| | -----------------------
| | By: /s/ M PARTON       
| |                        
| | Michael Parton         
| | Chief Executive Officer
|
| | Date: November 12, 2003

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