During its runs in Plymouth and London, Lovesong has had audiences reaching for the tissues in huge numbers. Penned by Abi Morgan (27, The Hour), produced by Frantic Assembly (Beautiful Burnout) and directed by Scott Graham and Steven Hoggett (the award-winning choreographer for Black Watch), it’s a delicately physical, intensely moving look at a couple’s relationship from two points in their lives: the early days of their marriage and the final ones.

One of its stars, lauded actor Siân Phillips, has been thrilled by the response: ‘I’m surprised because I thought, oh gosh I’m in the Frantic Assembly production that maybe isn’t going to appeal to young people, because they’re crazy about Frantic. But it really surprised me how well it’s been received – they laugh a lot but they’re very uninhibited about revealing their feelings. It’s quite amazing.’

Phillips, now 78, has been a fan of Frantic Assembly since 2001’s Tiny Dynamite, their first collaboration with Morgan. Despite initial fears that she wouldn’t be up to the task of performing their acclaimed physical choreography – which peppers Lovesong in small, emotional bursts – she’s found herself transformed by the show. But she’s still not sure why it’s left audiences so crippled with tears.

‘The young people in the audience,’ Phillips says, ‘they’re too young to have experienced the loss of a great love. Then again, an awful lot of people relate it to their parents. So I’m not sure – Abi pushes a lot of buttons and I don’t know what all of them are but it works.’

Citizens Theatre, Glasgow, Tue 7–Sat 11 Feb