Richard Tomkins has resigned as head of Sun Diagnostics in the UK after more than 20 years in the job. His departure appears to have taken Sun by surprise – no official statement has been issued – although a spokesman confirms that the company has begun the process of recruiting a new director.

The King's Lynn, Norfolk-based business is the engine diagnostics and emissions testing equipment division of the £1.28bn turnover US automotive tool manufacturer Snap-on Incorporated.

UK staff have been told that Tomkins has left to pursue other interests. While the search is on for a new chief, Sun's operations will be run by Amsterdam-based Brendan O'Malley, vice-president of Sun Diagnostics International and MD of Snap-on UK Holdings. Tomkins was not available for comment.