Early Advent, and I'm rattling about London's West End with an hour to kill. It's 8pm, freezing cold, and the pubs are bursting with hearty Cockneys. One of my favourites, the Lamb & Flag in Rose Street, carries a notice reading: "A pub is for life, not just for Christmas."

Mooching along Tottenham Court Road, I see that the small, anomalous business selling Barbour coats amid all the bookshops is displaying an "open" sign. I push at the door, but it's locked. The shop assistant lets me in, saying: "Come in. We keep the door locked for security reasons." He then locks it behind me. I do not want a Barbour; I have walked into the shop more to keep warm than anything. The man is now beaming at me, following me about the tiny premises.

"I'm afraid you haven't really got the kind of Barbour I'm looking for," I say. "And what kind is that?" asks the man. I notice that all the Barbours about me are rather long. "The short kind," I say. "Oh, but we do," says the man, as he unearths a phenomenally short Barbour jacket, "and these are reduced by £50!" "Well, I'm going now," I conclude, brutally.

In Great Newport Street, I notice - outside the Arts Theatre - a poster advertising James Campbell, a self-styled "stand-up comedian for kids". Having fulsomely praised Campbell in the Daily Telegraph a few weeks earlier, I scan the press credits: "My son was howling with laughter: Mail on Sunday"; "Brilliant: Evening Standard"; "Extremely funny: Guardian".

My ego bruised, I walk into Waterstone's on Garrick Street. After a quick glance at the shelves, I ask an assistant: "Have you got a novel called The Necropolis Railway?" Frowning, he types something into his computer. "Ah, yes, The Necropolis Railway by Martin . . . Andrew." He then walks to the fiction shelf, where he begins looking under "A". "I think you will find that your computer lists the surname first," I say, bitterly. So we go over to "M". The book is there, but in slightly the wrong place.

Now quite profoundly miserable, I thank the assistant. Two minutes later, I'm walking past the entrance to the Garrick Club, which is so opulent that it makes anyone standing outside feel like a Dickensian urchin. It's damned cold. I then remember that I have in my bag a lightweight coat I use for cycling. It's called a "Mac-in-a-Sack". I fish it out and put it on. I'm warmer now, but feel I must look like a trainspotter. Just then, the most elegantly dressed commissioning editor I know comes walking around the corner. He wears a blue double-breasted coat, suede boots and a red cashmere scarf.

"Andrew Martin, my dear boy!" he cries; then, peering at the label on my coat, "Mac-in-a-Sack! How cool!" I'm spending Christmas in Yorkshire and Scotland, and I can't bloody wait.