It is hard to convey the overwhelming awfulness of Love at the Lyric – a selection of badly sung pop song snippets by an over-age cast in a nursing home – but I’ll do my best. Instead of making you feel good about getting old, the show is the most powerful theatrical argument I’ve yet encountered for compulsory euthanasia.

The rambling ragbag is adapted by David Farr from an Icelandic “original” by the Vesturport directors Gisli Orn Gardarsson and Vikingur Kristjansson, and hinges on a late-blooming love affair between ancient Neville (Julian Curry) who suffers from dementia and a newly arrived widow (Anna Calder-Marshall) whose callous businessman son (Jonathan McGuinness) has dumped her in the home with an arm injury.

At one point the couple “escape” to the theatre – the Lyric, Hammersmith – fetching up in the front stalls to watch three crumbling inmates in black shawls perform an embarrassing sketch version of Chekhov’s Three Sisters. And Vesturport, incredibly, is the company which has dazzled us with such imaginative classical productions as Metamorphosis at this address and the waterlogged Woyzeck at the Barbican.

Something has gone seriously wrong with the musical direction, for none of the songs is completely performed, as if the copyright has not been cleared. So Jeffry Wickham ruins Lou Reed’s “Perfect Day” first by singing it atrociously and then by not honouring its musical architecture anyway. The same fault blights such gorgeous items as Blur’s “Tender” and Coldplay’s “Yellow.” The nearest we get to a full-blown choral rendition is Bowie’s “Life on Mars” but the plug is pulled on that, too, before we have take-off.

The community choir of local amateurs break out into shamefully under-rehearsed blasts of Cockney knees-up items like “Any Old Iron” and “Don’t Dilly Dally.” Their excruciating theatrical incontinence is highlighted by the pottering about of the old pros like Maria Charles and Dudley Sutton gazing vacantly on his Zimmer frame; Sutton’s Thomas has Alzheimer’s – so he’s a “nowhere man,” naturally.

When it’s not depressing or irritating, the event is monumentally crass. Why is a pianist in a red frilly shirt playing this stuff, anyway? And why is the implausibly attractive nurse (Hatla Williams) strutting around like a tart in between shouting orders like a camp commandant? None of it makes sense and I rushed home to grab a hot water bottle and a cup of Horlicks before being compelled to join in or sign up.

-Michael Coveney