Legend says that Britain will fall if the six resident ravens ever leave the Tower of London. It was enough of a premise for a bunch of East 15 graduates, an Essex acting school, to devise a play about the birds and their sense of duty to the Crown. They quarrel over biscuits, have a pecking order signified by the size of their perches, and flap around in distress when one raven goes missing: it is whispered that he escaped. Moreover, the Jubilee festivities are imminent and Queen Elizabeth will be paying a visit to the premises. The pressure is on.

Tangled Spider’s ensemble of seven assumes the birdlike body language well and manages to convince with minimal means – black outfits and a hint of feathers are enough. Sound behavioural study is betrayed by the way the flock now and again starts repeating words mindlessly, which is as funny as it is an accurate portrayal of the animals. They’re not stupid, however: collectively, they ponder on questions of faith and hierarchy only to go on and imagine life outside the Tower. Unable to fly (their wings are trimmed), the ravens are stuck with what they have, which not to all of them is equally agreeable. Inside the four walls, every bird has its place. Leader Edgar (Adam Bellamy), for instance, often plays dead because he likes to be the centre of attention, while Unknown (Eloise Levey) has a bad temper and is a bit of a gossip.

When a new face arrives (Mairin O’Hagan), she struggles to be accepted. Her aspirations are indeed aimed a bit higher than those of the rest: she is to be given to the Queen as a Jubilee present. Working day and night on her dance routine – intended to catch Elizabeth’s eye – the delusional bird fancies she is the reincarnation of another monarch and destined to live amongst royalty. It is but one of a number of imaginative, clever and funny devices that The Keepers has in store.

Born into duty, the ravens’ 15 minutes during the Queen’s procession are the peak of their lives. Once passed, the leader of the flock drops dead – and this time, it’s serious (probably).

Upstairs at The Oxford Arms on Camden High Street, Etcetera provides an intimate space of the kind in which fringe theatre blossoms. The show I witnessed was followed by another one in less than an hour, which reaffirms the sense of fleetingness and immediacy in theatre on this scale. I am happy I caught it: The Keepers is a pleasant fringe show with a heart of gold, and I wouldn’t be surprised if its life extended beyond the three days at Etcetera. Keep an eye on the listings.

The Keepers was playing Etcetera Theatre until 5 February. For more information, see the Etcetera Theatre website.