I remember joining Prima Volta so many years ago now that I can't ever remember when it actually was.... All I do remember was Simon asking me- well, we have this group.... its... well... ermmm, kind of a group- sort of .... just needs.... well.... some members :) good times..... we've been rehearsing together for years and in a few months we have some concerts to perform. 

I stand by the simple fact that it takes more rehearsals to prepare an all improvisation concert than any other type of performance :)