From a Gramophone review (June 2003 issue) by Ivan March of this DVD, of Rostropovich playing Shostakovich Cello Concerto 1 and the Prokofiev Symphony-Concerto:

When he came to know Shostakovich personally in the 1950s Rostropovich wanted to ask him for a cello concerto. Fortunately he never did: the composer's wife later told him that only if he did not ask or mention his wish might Shostakovich produce something out of the musical hat. She was right and in 1959 the great cellist's restraint was rewarded.

And what is more it was rewarded with another cello concerto, Number 2, which was also dedicated to Rostropovich. Not surprising, given how well he played the first one. That old recording he made for CBS (now Sony) with Eugene Ormandy and the Philadelphia Orchestra was one of my most treasured LPs.