His father Cyril Rootham was a well-known musician and composer based at St John's College, Cambridge.
His mother Rosamond Margaret Rootham (née Lucas) had been a notable suffragette, and continued as a campaigner on various social issues throughout her life.
In August 1934 Rootham played the cello in Michael Tippett's "people's" ballad opera "Robin Hood", conducted by the composer, at Boosbeck in North Yorkshire.
Anxious to play his part in the war effort, Rootham resigned from the Civil Service in 1941 to join the Special Operations Executive.
On completion of his training he was parachuted into eastern Serbia with a small team of British soldiers as part of the Mission Greenwood-Rootham.
However, the policy of the British government later changed, and UK support was switched from Mihailović to the communist partisans under Josip Broz Tito.
In 1945, Rootham was posted to Berlin where his fluency in Russian involved him in negotiations with the Soviet army in the run-up to the Potsdam Conference.
He was once heard to remark that he made more profit for Lazard in preventing unprofitable deals than in acquiring new business.
In 1975 the BBC broadcast one of Cyril Rootham's major works, his setting of Milton's poem Ode on the Morning of Christ's Nativity.