Hi:
A very curious piece of news. Quite astonishing.
Talking about his contribution to prog, I know he is mainly known by his orchestral versions of prog classics (Tull, Genesis...), but we can also notice he wrote some songs and made a few very good arrangemente. I like a lot 'Elegy', as well as the astounding 'Coronach', co-written by him (it's in the 20th Anniversary set). Both songs are very emotive. I think he also made the string arangements of 'Woman in the Wings', the Maddy Prior record. It'is not prog per se, but I recommend Tull fans checking it, specially the title track.
He surelly has made a lot of prog related works, but I sometimes mix his name with David Bedford, who has also arranged many orchestral prog songs.
Regards