Theatre-smiths is a new term to me, though it is an admirable description of the Plasticine Men collective, judging by Simon Day’s production of Keepers. It’s a taut piece of physical theatre, based on the true story of two lighthouse keepers in 1801 tending their vital lamp amid the lethal rocks of the Welsh coast.

Tomas Griffith (Fionn Gill) and Thomas Howell ([Martin Bonger) are very different in temperament and outlook. Howell is a bit of a martinet, using every actual or perceived lapse in duty on the part of Griffith to reinforce his superiority. When tragedy strikes, none of this is of any use to him.

Designer Samantha Keeble presents us with an almost-bare stage. There are two chairs, a grating, a ladder, oilskins and a light. Much is communicated to us through sound – not just words but bird noises, the drum-beat of the waves, the accelerating rasp of the gales (top marks to technical stage manager Anna Matthews) and incidental music from Lawrence Williams.

Then there is the mime, which is immensely effective. A seabird approaches and wings away, a man dies, fishes churn out of the foam, glass is cleaned, the perilous ascent to the lantern itself and descent to the rocks on which the structure perches are all made actual. Since Pixar, the word plasticine has ceased to denote merely a toy for children. In the creators of Keepers it is animated in many other senses.