The company (originally named Thomson Tour Operations (TTO), and renamed in 1997) was founded as part of the Thomson Travel Group in 1965 following the acquisition of four tour operators, Skytours, Riviera, Gaytours and Luxitours and the airline Britannia Airways by Roy Thomson.

Intense competition continued between the four acquired operators which allowed the rival Clarksons Travel Group to become the lead player in the new and rapidly expanding UK package holiday market, while Thomson initially lacked any effective strategy to fight back. But in 1971, following the appointment of Brian Llewellyn as TTO’s 7th Managing Director, a whole new Board of Directors was created, with the travel trade veteran Norman Corkhill as company chairman. A clear strategy was now implemented, as part of which the businesses were re-branded and re-launched under a single name as “Thomson Holidays”.

Info gleaned from Wikipedia