On a whim on Sunday morning, I took the train to Oxford. And, as always - it's only an hour away - I wondered, why don't I do this more often? Once I'd doused myself in colour, and visited the Ashmolean, I ambled about the city for a couple of hours soaking up centuries of history. And literature. (And I always feel a pang. If only I'd worked a bit harder when I was at school...)

I thought about having a pint at the Eagle and Child, which ought to be wreathed in a blue fug of pipe smoke, and I thought about the Inklings - Tolkien, CS Lewis and his brother Warnie - who met in the back bar every Tuesday morning to drink beer. And talk. You wouldn't be surprised if you saw Frodo Baggins and Strider sitting in the snug.

I walked down Cornmarket, past an inn where Shakespeare often stayed - and tumbled the inn-keeper's wife - on his way up and down between Stratford and London. (In Pizza Express next door, there's a Painted Room looking much as it would have done in Shakespeare's time. Ask nicely. They won't make you buy a pizza.)

I walked across Tom Quad - where Brideshead's outrageous aesthete Anthony Blanche was thrown into the fishpond - and was in time for evensong at Christ Church. Then I strolled through Christ Church meadow thinking about Alice and her sisters scampering down to the river to hear a story. And Lewis Carroll, dining at High Table in the splendid college dining hall, and seeing Alice's father, the Dean of Christ Church, disappearing down a narrow spiral staircase every night ... rather as if he were vanishing down a rabbithole?

And I think that Lewis Carroll and Alice would be absolutely delighted that, more than a century later, that same hammerbeam roof was bewitched to look like a sky dotted with stars - that flickering candles hovered in mid-air - and that Dumbledore and Professor McGonagall were sitting at High Table. Because Christ Church dining hall was the inspiration for Hogwarts in the Harry Potter films.