A very good and probably important guitarist. His later stuff gets a bit too shreddy for me but anything up to 1972 works fine. Also, often features Harry Beckett which means you can't go wrong. He also plays in Beckett's Joy Unlimited band.
Try 'Dragon Hill' for a good starter. There's a couple of recent very good releases on Jazz In Britain which should be streamable.
As to why so few recordings form the ICA? I have no idea, too many Happenings instead