Tomkinson, who won The Roux Scholarship in 2005, joins from The Montagu Arms hotel in Beaulieu, New Forest, where he headed up the Terrace restaurant for 10 years.
His new role will see him open a 50-cover restaurant, Betony, at The King’s Head in March.
Tomkinson told BigHospitality: “Betony will have a relaxed, casual feel with an a la carte menu and a surprise tasting menu. We will also be offering great bar food in the King's Head bar.”
The chef says he is hoping to make contact with some local suppliers in the next few weeks to start developing the menu.
Tomkinson won a Michelin star while cooking at The Goose in Britwell Salome, Oxfordshire in 2008.
He held a star at The Terrace at The Montagu Arms for eight years, but it lost the award in 2016 while undergoing a major refurbishment.
Chef Matthew Whitfield has replaced Tomkinson at the Montagu Arms, six years after he first worked at the restaurant as head pastry chef.