Ben-Hur, the movie, featured the largest film set ever constructed and 10,000 extras; it lasted three and a half hours, and won 11 Oscars. Ben Hur, the play, has four actors and some wobbly plywood. Happily, it also has a lot of pluck. Patrick Barlow, repeating the trick he pulled with his adaptation of The 39 Steps, is fulfilling a childhood dream - he's long loved the Biblical epic, both the movie and Lew Wallace's original novel. But there's no reverence whatsoever here, thank Christ (a figure who turns up not infrequently, in fact) - this is an extremely silly, but very enjoyable, parody.

The conceit is that this stage version of Ben-Hur is a vanity project of luvvie writer-director-star, Daniel Vale. He's played with deliciously ripe fruitiness by John Hopkins, who also perfects the tremulous deep voice of the Fifties studio star when playing - who else - Judah Ben Hur. His ambition is not matched in production values. Cues for bombastic music go awry, costumes get trapped in bits of set, quick-changes go horribly wrong, and the cod-historical script is garbled (especially in the mouth of the wonderfully, wearily confused Richard Durden, who tells us the baby Jesus is born in a "fumble humble stable stumble Dumbledore.") In tiny tunics and plastic moulded armour, the homoeroticism (which reeked off the original, of course) is suitably high, and there's much of cross-dressing and many dodgy accents.

The first half takes a while to find its rhythm, mind. Although much of the audience appear to collapse in hysterics at the first comedy camel puppet they see, I find it's a while before the laughs are coming thick enough. Amateur actors and backstage comedy are well-worn targets, and the tone often veers more towards dodgy panto then smarter fare like Noises Off. The comically crap take on an epic is hardly new either - think Monty Python, or even other acts of compression like the Reduced Shakespeare Company.

But you'd have to be po-faced indeed not to get caught up in it - especially as the audience are literally enlisted. To recreate gruelling scenes aboard a slave ship, The Tricycle is divided into galley slaves - told to mime rowing; obeyed with gusto - and Roman slave drivers - instructed to shout 'authentic' Roman abuse: "do get a shift on, we've got to be in Syracuse by teatime!"

And the second half really gallops: the pace picks up, as does the gag-rate, while the famous chariot race is both suitably daft and more impressive than you expect. Tim Carroll's direction finds its edge, and there are OTT, exhausting-looking performances from all four of the cast. Meanwhile, Daniel Vale's romantic jealousies, and parent issues, gradually underscore and interrupt the increasingly haywire Ben Hur production, adding - well, not depth exactly, but a more satisfyingly dramatic experience. The ending, in which Jesus arrives to patch things up with love and forgiveness, even manages to make this mock-Roman epic suddenly feel imbued with the magic of Christmas.

It's great programming: Ben Hur may be as lightweight as its plywood sets, but 'tis the season for pure entertainment. It makes a nice alternative to traditional panto or more sentimental festive fare, with groansome puns and knowingly-naff innuendo to keep grown-ups happy, and an anarchy of mishap and wanton destruction that kids will respond to.

Ben Hur runs at the Tricycle until 9 January.