They came brandishing cutlasses, wearing black eye-patches and tricorn hats flaunting that potent emblem of the pirate’s trade, the skull and crossbones.

Well, fliers had urged us to put on suitable attire for the Watermill’s Treasure Island, and most junior members of the audience — and not a few senior ones, too — duly obliged.

In line with its long-standing tradition, the theatre supplies festive entertainment which, while not being a pantomime, still offers a deal of excitement, spectacle, music and opportunity for spectators to become involved. In respect of the last, nothing I shall see from the stalls in the next couple of weeks is likely to compete fun-wise with this show’s chance to hurl boulders (foam rubber boulders, I hasten to add) at Long John Silver’s pirate gang.

This intervention is necessary in order for right to triumph in a version of Robert Louis Stevenson’s adventure which at this point leaves Emily Butterfield’s Jim Hawkins with no allies against the mutineers. Other members of the six-strong cast are occupied being villains at the time.

Readers will have noted that cabin boy Jim is played by a girl. In fact, Emily (pictured right) portrays a modern-day miss of the same name. She dreams of being a pirate; indeed, dreams up the whole story which is presented, true to the original, but as if invented ‘on the hoof’ as the action proceeds. This framing device — while it sounds complicated and could baffle the very youngest members of the audience — in fact works very well. For one thing it permits droll commentary on the story by those engaged in telling it.

And a very talented bunch they are, multi-tasking on assorted musical instruments in the Watermill’s recognised house style as they present the famous gallery of characters. Besides Emily’s winning hero/heroine, we see excellent work from Howard Coggins as Dr Livesey (conflated in Toby Hulse’s clever adaptation with Squire Trelawney), Patrick Driver as Long John Silver, Nicholas Goode as Captain Smollett and Morgan Philpott as Ben Gunn. I mention only iconic characters. Katherine Toy has no icon, but plays a full part as Jim’s mum and later as Patrick O’Brien.

Ably directed by Robin Belfield and with first-class music by Simon Slater, the show is on till January 2. Box office: 01635 46044 (www.watermill.org.uk).