Crocosmia is a theatrical gem: warm-hearted but never soppy, liberated yet finely controlled, and imaginative but never once getting lost in its own ideas. It is a show whose themes are bound up in its very fabric, which means the company can hint at big ideas about family, dependency and love, whilst still having a whole lot of fun in the process. It also contains a scene in which an entire Battenberg cake is systematically and unfathomably stuffed inside one actor’s mouth, to the point his cheeks look fit to explode. That this moment proves touching and expressive, as well as gleefully funny, tells you a lot about the depth and spark of this resourceful and impressive show.

This is a play about family and about love, though it isn’t nearly as laboured and sentimental as that might sound. The show opens on three siblings – 10 year old twins Sophia (Shamira Turner) and Finnley (Dominic Conway) and their younger sister Freya (Clare Beresford) – larking about on stage, accompanied by their parent’s vintage CD collection, delving into and delighting in the props. It is like watching a lazy Saturday morning on fast-forward, as the children jump from one activity to the next, their curiosity never quenched, their energy unchecked and their imagination unfettered.

As we watch the three actors bound about on-stage, carving goldfish out of carrots, creating beards out of shaving foam, making magic out of next to nothing, we are swiftly and unthinkingly sucked into these children’s lives. The makeshift feel of their activities and their surreptitious glances to their audiences – those imploring looks that cry out ‘love me!’ – lend the show the feeling of an impromptu family concert. The audience unwittingly adopts the role of proud parent, watching anxiously from the wings and willing these precocious but endearing kids to succeed.

It might be slightly manipulative, but who cares when it’s this much fun? Furthermore, this familial dynamic – this heightened bond between audience and actors - takes on a much deeper significance half-way through the show. We watch the two twins dress up, once again, as their parents, but rather than re-construct some fond memory, or re-enact a silly and touchingly faux ‘grown-up’ scene, the two children remember a tragedy. We learn their parents have died in a car crash and that this play-acting isn’t as carefree as we imagined; that it is about survival and about maintaining some semblance of reality, when everything familiar and comforting has been unexpectedly torn away for good. The audience’s role as doting parent is cemented with this revelation, as we realise these children are not just performing to us, but to the memory of their parents. Their need to be liked by us parallels their need for new parents and the audience, willingly and warmly, tries to plug this devastating gap.

This tacit support between actor and audience means that even the inevitable audience-interaction segment feels fresh and packed with good-will. Near the end, the older twins arrange a surprise birthday party for young Freya (one of the most committed, complete and downright endearing performances I’ve seen in a long time) and hand out poppers and balloons to the audience’s outstretched hands. One could sense the crowd tingling, bustling in anticipation – exactly the same feeling one might experience at a real-life surprise party – and the audience’s genuine desire to cheer up this frightened but brave little girls is testimony to the authentic charm of this delicate and quietly moving show.

Till 26 September 2009