The boss of the UK's largest pub company has joined the Café Rouge and Bella Italia owner at a time when he and Tragus are both pondering their future.
Earlier this month Tragus appointed corporate financier Close Brothers to consider its options, including a £200m stock market flotation.
Tragus is led by chief executive Graham Turner and 85% owned by venture capitalist Legal & General Ventures
Turner said: "Today's announcement marks an important moment in time for Tragus. Giles's considerable experience across many areas of the leisure sector along with his extensive corporate development experience will provide us with unrivalled expertise and counsel."
Last month Thorley said he might quit Punch within 18 months as he didn't see himself going on in his current role "forever". He joined the pub company in December 2001 as executive chairman.
By Chris Druce