First, let's get the good bits out of the way. Three professional actors have joined a community cast of 60 plus The Shysters, a group of actors with learning difficulties, for this new musical.
It seems as though everyone has had a really good time doing it. There's lots of energy and some members of the community cast have excellent voices.
The bad news, though, is that the show itself is dreadful. You get a sense of what you're in for from Chris Bond's tediously worthy text in the opening number, with Queen Isabella and an all-dancing, all-singing company of monks and nuns enthusing about going off to do a spot of "ethnic cleansing".
If only we could all be more sceptical about what we're told, the show platitudinously concludes, there wouldn't be any more Spanish Inquisitions. Or modern British musicals, it's tempting to add.
Matthew Kelly, who was born to play Don Quixote, introduces a much-needed note of dignity and charm as the bookish, flowery-tongued old knight set adrift in a hostile society (he should try Blair's Britain).
George Costigan, clowning along as his faithful servant Sancho Panza, is a good actor but I have to tell the truth: he can't sing for toffee.
Fortunately several of his amateur colleagues can, and Rosie Kemp has the best song, the folksy What If. But most of Jo Collins' music is humdrum at best, and it's only in a few of the ensemble numbers - there's a panto-style episode with a bunch of here-we-go English pirates, for instance - that the sheer energy level transcends the general feeling of tedium.
* Running time: Two hours 20 minutes. Until July 9.