Sambrook is currently global account director at Accenture Marketing Services, which bought Billetts' main rival Media Audits in November 2005.
He joins Billetts as a managing partner of its global division on 18 February, as the business looks to expand internationally, including into emerging markets India and China. Sambrook will report to Nick Manning, recently appointed as chief operating officer of Thomson.
His appointment follows a restructure in November when Martin Wright the former president of FCBi Europe, joined as managing partner of Thomson's media monitoring unit.
At the same time, Andy Pearch, the former chief executive of Billetts and commercial director of Thomson Intermedia took on the new role of managing partner for content and data integrity.
Billetts was bought by Thomson for £13.1m in August 2005, three months before Accenture's acquisition of Media Audits.