Mastermind returns this week (xxdays at yy on BBC2), and brings back the sensation of a curtain coming down in front of my brain. Eighteen months ago I was invited to take part in a programme of Celebrity Mastermind, with Vic Reeves, Janet Street-Porter, and Jonathan Meades, being quizzed by Magnus Magnusson. Magnus was an old friend - I was delighted to see him again - and the whole event was great fun, but even so the experience was as intimidating as a vital exam or a job interview.

Before the audience came in we had a rehearsal, so that we would know what to do when, and I remember Vic sitting in the dreaded black chair. 'What is your name and your specialized subject?' Vic paled, and said 'Er...' He couldn't even remember his name. I thought that was ridiculous, until my turn came. I heaved myself to my feet, walked across the stage to the black chair, and sat down. The lights dimmed, the music sent shivers up my spine, and as Magnus spoke it really felt as if a dark curtain had come down between me and my brain.

I did well in my specialized subject, but hopelessly on general knowledge; that curtain cut me off from my memory.

Mastermind always seemed the perfect quiz show. No fancy flashing lights or special effects. No cash prizes. Just Magnus, the dim light, the eerie music, and the victim in the dreaded black chair. The contestants seemed both ordinary - from taxi-drivers to diplomats - and also extraordinary in their unbelievable knowledge of seventeenth-century hairstyles or left-handed Wimbledon umpires. For week after week I sat transfixed, and wondered whether I could ever hope to take part - and then when I did get the chance, I blew it. How could I not know that those patterned socks are called Argyle? How could I forget that St Ives is the arts centre of Cornwall? I blame that curtain.

I watched again when my  programme was repeated, but I did no better the second time... Jonathan Meades won, and I came second equal with Janet Street-Porter.

Magnus was avuncular - warm and encouraging. I suspect John Humphrys is a wee bit more inquisitorial - a shade nearer the abrasive Paxo. I shall sympathise with the new contestants, and wish them well from the safety of my sofa at home.