Unlike many theater troupes performing today, Britain’s Kneehigh Theatre — the company behind last year’s The Wild Bride and Brief Encounter — appears hell-bent on making sure you have a good time. This time it’s with one of the oldest love stories on record. Tristan & Yseult, which is now in production at Berkeley Rep (1915 Addison St., Berkeley), involves a tragic love triangle between warrior Tristan (Andrew Durand), his Uncle, King Mark of Cornwall (Mike Shepherd), and Yseult (Patrycja Kujawska). Adapted and directed by Emma Rice (Brief Encounter, Oedipussy), Tristan & Yseult creates a collision of spectacle, storytelling, circus, music, dance, and comedy to delight and challenge our conceptions of what “theater” can be. The result is as jubilant and fun as it is moving and heartfelt. The humor is clever, restrained, and unsurprisingly British, with a rolling emphasis on slapstick, dragtastic drollery, and the subdued gaiety that can only come from men dressed in funny hats. Do yourself a favor and go see it.