I spend quite a lot of my life shuttling between home and theatres on the North London line which runs from Stratford in the east to Richmond in the west. It's a much improved service, with an offshoot now to Clapham and Shepherd's Bush.

Going east, I find myself conveniently deposited near the King's Head, the Almeida, the Arcola, the Hackney Empire and Stratford East itself; heading in a westerly direction, I can visit the Tricycle, the Orange Tree and the Richmond Theatre.

These journeys break up the Groundhog Day routine of travelling on the Northern Line into the West End, a routine I vary anyway by hopping on the 24 bus. And last night, heading towards the Almeida for Stephen Poliakoff's intriguing new play, My City, I found myself strap-hanging next to the actor Sam Troughton.

"Where are you off to?" I enquired. "I'm going to see dad's first night." "Oh, what's he in?" "The new Poliakoff play at the Almeida." Of course he was. And very fine, too, bursting at the seams, almost, with the fineness of his acting.

I had spent the afternoon with half an ear turned to the radio for the climax of the county cricket championship in which Sam's elder brother, Jim Troughton, was a key player: as captain of Warwickshire he was on the brink of the most glorious day in his career (apart from playing for England in a series of one-day games some years back).

It wasn't, alas, to be. Warwickshire simply couldn't bowl out Hampshire a second time round on a flat pitch at the Rose Bowl; Lancashire meanwhile secured a famous win over Somerset at Taunton, and their first outright championship since 1934.

David is one of five children. His brother, Michael, also an actor, Sam's uncle, is completing a biography of grandpa Patrick Troughton, the second Doctor Who, in succession to William Hartnell in the 1960s. So this is one of the most interesting theatrical dynasties we have, though not as well known perhaps as the Redgraves or the Cusacks.

And guess what, there was a Cusack on stage alongside David last night, too, the wonderful Sorcha Cusack, sister of Sinead and Niamh, though with rather less to do in the play than David.   

And what of Sam himself, recently an acclaimed Brutus and an impassioned, unusual Romeo (in Rupert Goold's production) with the Royal Shakespeare Company but now finished with the RSC's three-year ensemble? Life's no different than for any other actor: a lull, an interim, and an endless round of auditions...

It was good to see Tracey Ullman back on stage in the Poliakoff, playing a mysterious teacher who takes her former pupils on a switch back ride through London and her own battered psyche.

She's lost none of her canny stage craft, though her comic personality is much suppressed. I last saw her, over twenty years ago, playing Kate in The Taming of the Shrew in Central Park, New York, opposite Morgan Freeman. I'd like to see some of that spitfire comic talent unleashed again.

As usual at an Almeida first night, there was a good turn out of alumni and other notables. I was fascinated at how discreetly new young superstar Carey Mulligan slid through the foyer and into the auditorium.

She's not announced in the cast of the next production, Neil LaBute's Reasons To Be Pretty, so she was obviously on hand partly to lend support to her friend Tom Riley who's in the cast. (Check out Dan Wooller's delightful first night photos of Carey for Whatsonstage.com)

And talking of dynasties... there's another one on its way. The waitress in Poliakoff's underground Sunquest club is played by professional debutant Hannah Arterton, who just happens to be Gemma's kid sister. Will the line stretch out to the crack of doom?