The writing of Larchfield has led so many wonderful experiences. First among them  is the discovery of Auden’s life in Helensburgh, which is at the heart of the book. It gave me such joy and creative satisfaction to discover Auden (whose work I did not know well), and to imagine him so completely as the awkward young man of twenty four who came to live in my home town and had so many formative experiences there. I found in Auden, and the way his story intertwined with that of my heroine, Dora, great solace.

This period in Auden’s life has been only superficially documented. Helensburgh is a long way from where his biographers lived, and only gets a cursory few lines. But the Auden that taught at Larchfield school was already a fully formed artist and visionary, and has become newly timely, with his meditation on repression and political uncertainty, The Orators. BAFTA winning director Adam Low is creating a documentary about Auden, centring on this idea of a ‘New Age of Anxiety’ where Auden offers new solace and insight in troubled times. Writers taking part include Alexander McCall Smith, James Fenton, Alan Bennett, and now me.

A few weeks ago Adam Low, Martin Rosenbaum and John Archer descended on Helensburgh and Larchfield school to film the Auden landmarks and interview me about the writing of Larchfield and how encountering Auden as I did changed my life. It was my first experience of being directed, and by a master of the documentary genre. Adam is a brilliant — yet invisible to the camera — interviewer. He and Martin, so painstaking behind the camera, are a unique team. The experience was not unlike being properly edited by those at the top of their game, as I was for Larchfield. The physical result was also the same, needing to take to my bed for a full day afterwards, completely drained!

There is so much standing around with filming, and then the magic happens. An abiding memory for me is when we waited with Martin for the right light to cross the front of Larchfield school. We waited for an hour and a half. The clouds kept coming at just the wrong moment. Martin and Adam displayed the zen-like patience of the true artist, and we were finally rewarded, with a burst of golden sunlight that transported the scene right back to 1930 and the moment I imagined Auden walking out of the front door. It was quite emotional. I quietly wiped a sentimental author tear.

The finished documentary will be screened on BBC2 on Saturday 30 September at 9pm.

Outside Larchfield just as the sun broke out. Thank you John Archer for this.

Masters at work, Martin and Adam find a new view of Helensburgh station, site of a key moment in Larchfield, where Wystan glimpses his new lover for the first time