**EXHIBIT 31.1****CERTIFICATION OF CHIEF EXECUTIVE OFFICER**Pursuant to Section 302 of the Sarbanes-Oxley Act of 2002 I, STEPHEN J. SILLS, certify that:1. I have reviewed this Annual Report on Form 10-K of Darwin Professional Underwriters,Inc. (the “Registrant”);2. Based on my knowledge, this report does not contain any untrue statement of a material factor omitto state a material fact necessary to make the statements made, in light of the circumstancesunderwhich such statements were made, not misleading with respect to the period covered by thisreport;3. Based on my knowledge, the financial statements, and other financial information includedin thisreport, fairly present in all material respects the financial condition, results of operationsand cashflows of the Registrant as of, and for, the periods presented in this report;4. The Registrant’s other certifying officer and I are responsible for establishing andmaintainingdisclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e))andinternal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and15d-15(f))for the Registrant and we have:a. designed such disclosure controls and procedures, or caused such disclosure controls andprocedures to be designed under our supervision, to ensure that material information relatingto the Registrant, including its consolidated subsidiaries, is made known to us by otherswithin those entities, particularly during the period in which this report is being prepared;b. designed such internal control over financial reporting, or caused such internal controlover financial reporting to be designed under our supervision, to provide reasonableassurance regarding the reliability of financial reporting and the preparation of financialstatements for external purposes in accordance with generally accepted accounting principles;c. evaluated the effectiveness of the Registrant’s disclosure controls and procedures andpresented in this report our conclusions about the effectiveness of the disclosure controlsand procedures, as of the end of the period covered by this report based on suchevaluation; andd. disclosed in this report any change in the Registrant’s internal control over financialreporting that occurred during the Registrant’s most recent fiscal quarter that hasmaterially affected, or is reasonably likely to materially affect, the Registrant’s internalcontrol over financial reporting; and5. The Registrant’s other certifying officer and I have disclosed, based on our most recentevaluation of internal control over financial reporting, to the Registrant’s auditors and theaudit committee of Registrant’s board of directors (or persons performing the equivalentfunctions):a. all significant deficiencies and material weaknesses in the design or operation ofinternal control over financial reporting which are reasonably likely to adversely affect theRegistrant’s ability to record, process, summarize and report financial information; andb. any fraud, whether or not material, that involves management or other employees whohave a significant role in the Registrant’s internal control over financial reporting.        Date: February 23, 2007 /s/ Stephen J. Sills   Stephen J. Sills, Pres. & CEO