##### 



Exhibit 99.1

I, Jeroen van der Veer, certify
that:


|   |                                                                                                                                                                                                                                                                                                                           
|-- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
|1. | I have reviewed this Amendment No. 1 to the
    annual report on Form 20-F of Royal Dutch Petroleum Company
    (N.V. Koninklijke Nederlandsche Petroleum Maatschappij);                                                                                                                                                  
|  
|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;
|  
|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;                      
|  
|4. | The companys other certifying officer 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:                                                                                         



| |     |                                                                                                                                                                                                                                                                                                                                                                                                    
| | --- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| | (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;
|
| | (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                                                                                                   
|
| | (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;                                                                               



|   |                                                                                                                                                                                                                                                                                                       
|-- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
|5. | The companys other certifying officer 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):



| |     |                                                                                                                                                                                                                                                                                       
| | --- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| | (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
|
| | (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.                                                                                                       







/s/ Jeroen van der Veer


--------------------------------------------------------------------


Jeroen van der Veer


President and Managing Director




May 4, 2005



E 2 Royal
Dutch/Shell Group of Companies


20-F/A (Amendment No. 1) 2004