Here he comes, mister whiz – celebrating Stephen Sondheim at 90

My oldest son has just discovered Stephen Sondheim. Or at least, he is on the verge. He saw the film Marriage Story and afterwards listened to Adam Driver singing "Being Alive" on repeat for about three days. That was fine by me; he has been snared. I am now sneaking Follies and Sweeney Todd onto the sound system. He will soon be unable to live without a daily dose of Sondheim.

I can't remember when I first got hooked, but I think it was thanks to Millicent Martin. I was vaguely obsessed with her in the late 1970s (also for reasons that remain obscure) and so one day on a trip to London, I got a standby ticket to sit in the vertiginous gods at the Garrick Theatre to watch Side By Side by Sondheim, a revue invented by Ned Sherrin, produced by Cameron Mackintosh and starring Martin, Julia McKenzie and David Kernan.

That was it. Instant love. I think, looking back, the show made me feel sophisticated and clever. All those smart lyrics, those twisting rhymes, the way that songs wind round on themselves and end up telling an entire story of a life. The show was the perfect introduction because it told you why the songs mattered, giving a little history of their place in shows that I had never at that point seen or read about.

But what really touched me was the melancholy running underneath the wit, the quiet desperation that fuelled songs such as "Losing My Mind", "Send in the Clowns" and "Anyone Can Whistle". From that point, I was a Sondheim addict, catching each show as it appeared, quite often having listened to the cast recording until the grooves wore out before I actually had a chance to see it.

It's odd to think now, when the Sondheim musicals are so firmly enmeshed in the English repertory, that once upon a time it was regarded as rather strange to like him in the 1980s when British stages – and indeed Broadway – were dominated by English musicals such as Cats, Phantom of the Opera and the juggernaut that is Les Mis. If you loved Sondheim, you were member of a weird cult rather than a mainstream musicals fan.

Friendships were forged over memories of the British premiere of Sweeney Todd at Drury Lane in 1980 – almost universally greeted with bad reviews but an absolute revelation to me, with performances by Sheila Hancock and Dennis Quilley that have stayed in my mind forever; eternal bonds were strengthened by long appreciative conversations about the filmed concert performance of Follies in 1985, which sent me into the back catalogue of the wonderful Lee Remick and has made me follow the career of Mandy Patinkin ever since.

Like all geniuses, Sondheim sends you scurrying in different directions to discover more about the things he loves and the people who adore him. Barbara Cook was in that concert performance, and through her I discovered a rare interpreter of the American songbook, and many magical nights in the theatre in her company. Sunday in the Park with George encouraged more study of Seurat, who'd I'd always dismissed as an Impressionist also-ran, just as A Little Night Music made me explore the films of Ingmar Bergman. Assassins remains the basis for my knowledge of the killers of American presidents.

Through it all ran the tunes. It always amazes me that people say Sondheim can't write tunes: "Music and Art" can linger in my head for days, the gentle magic of the lyrics twining around those delicate tugging chords; "Barcelona" combines melody and wit to devastating effect; "Every Day A Little Death", built like an aria from an operetta, takes its power from the way its savage dissection of a human relationships is built around an intricate structure of rising and falling notes; "Being Alive", as my son noticed, is both lyrically majestic and melodically catchy.

I find it hard to choose favourites because each song and each musical is so wrapped up in so much of my theatregoing life. Even the shows that people don't like are full of memories to me: I went to Leicester with a group of friends to see the professional UK premiere of the much-maligned Merrily We Roll Along in April 1992, 11 years after its disastrous US premiere. It was still a difficult musical to adore, but Maria Friedman was there singing "Not a Day Goes By", so there wasn't much to complain about.

This week, one of those friends and I had booked to go to New York to see the Broadway premiere of Marianne Elliott's magnificent rethinking of Company, with a female Bobby. It was going to open on Stephen Sondheim's 90th birthday. I am so sad that COVID-19 means none of us will be there, but celebrate still every single one of the memories that Sondheim has bequeathed to me (interviewing him on stage at the National Gallery for the revival of Sunday in the Park in 2005 was a particular joy, as you can imagine.)

And go on then, if you really push me, I can choose three Sondheim musicals that I can't live without: Company, Follies and Sweeney Todd, probably in that order. And the song? "Losing My Mind". As sung by Cook.

You can listen to it below.