Pirates, mermaids, monsters, magic, singing and dancing, all served up on a bed of real sand; this ambitious promenade show from the Unicorn Theatre and NIE combines an impressive range of ingredients, drawing together the stories of children from Southwark, Lambeth and Waltham Forest about the river Thames. The choice of venue is a masterstroke; a slimy, dripping brick tunnel under London Bridge does much to create an atmosphere of watery mystery, with its curtained-off nooks and side tunnels ready to be explored. If the acting sometimes smacks a little too much of the theatre’s stablemates under the arches, the London Dungeons and the London Bridge Experience, the exploratory magic of being summoned to a sing-song in a bar run by a pirate or down a secret passageway marked on a treasure map easily snaps us out of the half-term museum shuffle.

Without the lulling properties of soft seats and theatre dark, the children are wide awake and desperate to engage. This is lovely, but also dangerous when so much of what this show is asking them to do is to listen quietly. Their surplus energy spills out in irreverent questions and pre-teen sass which the actors are more than equal to handling, but could do with more outlets.  When we were randomly split into groups and sent separate ways, participation was jettisoned in favour of more static storytelling. I can see the wisdom of giving children stories to swap on the schoolbus home, but it seems strange to dictate to, rather than improvise from, the ideas of a small, incredibly excited audience.

What’s really needed here is a strong, overreaching frame narrative, whether historical or imaginary, to link the stories and to explore what storytelling means, but the tunnel wall we pass papered with children’s stories is emblematic of an attitude that seems to see stories as raw material to be churned out by schools rather than living, evolving things. The New International Encounter theatre company tours globally, with a wide base of actors from different countries, but strangely, no effort is made to give an international perspective on the role of the Thames in trade and shipping, as a melting pot of different cultures reaching centuries back. Instead, the nameless pirate-landlord, looking like driftwood from the Spanish Armada, quips “I don’t even know if this is my real accent”, before finding his origins in a tale that inexplicably seems to take place centuries later, during the Silver Jubilee flotilla.

Keeping children focused in a tunnel full of enticing distractions is an achievement, but sometimes the actors seem happy to undermine their own created world for laughs; while adding deliberate anachronisms is fairly harmless, encouraging the audience to get through participation elements quickly and making fun of the more fantastical elements of the script sacrifices integrity for accessibility. Still, if we don’t learn much about tale-telling or the river Thames here, for sheer entertainment value this show is a ship well worth sailing in.

Tales From The River Thames is playing at the Unicorn Theatre until 23 June. For more information and tickets, see the Unicorn Theatre website. Photography by Claire Haigh.