If it counts, he did that soundtrack music together with Mike in 1978. I think Tony has stated at some time he is "terrible" at guesting for other artists.
It doesn't.
Banks in 1983: "I used [From The Undertow] in a film I did called The Shout and that was the main theme. It was used extremely badly, but I thought the film was good."
Anthony Phillips on The Shout in 1981: "They [Banks and Rutherford] weren't happy with that. Mind you, neither was Rupert Hine. He got credited with "electronics", but he did a lot of background music. [Banks and Rutherford] did the theme, and one or two other bits, but he did most of the background music, and just got credited with electronics."
I don't recall that Banks quote about guesting. And I cannot see how he could say it, given he's not really done it. He must have been asked innumerable times.