According to the King's Head website (
here), it's "Collins' own stage adaption." Hmm - looks interesting. At 7 quid a ticket, certainly seems worthwhile.
Bit hard to find on the KH website - it's under "What's On," then "Sunday/Monday Night Shows," then "Forgotten Classics." No information on casting, however (and none on the
primaveraproductions.com website either).