When marathon hopeful Mark fails to make the cut for team GB, his girlfriend suggests he act as a guide for blind runner Becky. In Hollywood’s hands Tether could so easily be an over-sentimental tale of self-sacrifice, but Isley Lynn’s script focuses instead on the raw ambition of competitive athletes. Mark wants gold, Becky wants a higher placing and they’re both selfish in the pursuit of their goals.

Tether provides a fascinating insight into this unique sporting partnership as well as athletes with a visual disability. Becky notes that, as a woman, being blind isn’t her biggest challenge. Her dry sense of humour and disparaging remarks as Mark attempts to guide her provide regular comic relief but it’s not until late in the play that the pair have a chance to unleash strong emotions in a tense and furious argument.

Unsurprisingly in a play about runners, Tether is an impressively physical performance. Both cast members spend the majority of the play running on the spot, delivering their lines between deep breaths. Spot lighting and pulsing beats coupled with increasingly pained faces create convincing marathon montages but the big race scenes fall a bit flat, so similar are they to the training runs.

Underbelly Cowgate, 0844 545 8252, until 30 Aug (not 17), 2pm, £9–£10 (£8–£9).