Heard tonight on the radio, from memory: In the mid-1950s, William Walton was living with his much younger wife on the island of Ischia. The Russian cellist Gregor Piatagorsky, then on the West Coast of the US, wrote him asking for a cello concerto. He responded that being a professional composer, he wrote better when paid. And he added that he wrote much, much better when paid in dollars.
Evidently arrangements were made, since his Cello Concerto is playing now on the wireless.
Sounds like Walton's humour.