This time last year, Just Stop Oil protestors interrupted a performance of Les Misérables. They reasoned a musical about rebellion was the right place to protest about the impending climate catastrophe. To Save the Sea is also a musical about resistance, but there is no cause for a skirmish. It makes the environmental point brilliantly enough on its own.

Written and directed by Isla Cowan and Andy McGregor for Sleeping Warrior, it is a through-composed tribute to the Greenpeace occupation of the Brent Spar oil store in 1995. In today’s pessimistic age, the action stands as a beacon of climate activism; for all its precariousness and near defeat, it made a difference.

After Brent Spar had fulfilled its purpose, Shell had intended to dump its toxic remnants in the North Sea. Prime minister John Major was on side. The German chancellor, Helmut Kohl, was not. The Greenpeace occupation captured the imagination of consumers. Shell had the muscle to dispense with the protesters but not the resources to deal with a boycott. The people won out.

Spotting the potential of this David-and-Goliath conflict, complete with its high-seas drama, Cowan and McGregor field an eight-strong company in a show that bulges with ambition. Where the activists belt out strident musical-theatre anthems with titles such as One Foot in Front of Another and Bring It On, their opponents trade in comic show tunes, the better to send up their roles as villains of the piece. The songs are clear and catchy, giving not only emotional heft to the activists’ commitment but also a sense of jeopardy – not to mention the sting of satire.

It would be great to see the show taken up a scale: it calls out for a live band. But as it stands, it is a galvanising ensemble piece. Staged on a rugged gantry designed by Claire Halleran and dramatically lit by Simon Wilkinson, it has heart, humour and political nous.