NOW I know how Norman Stanley Fletcher must have felt. Or do I?

After all, I suspect my brief spell in Porridge might not necessarily reflect the true experience of Ronnie Barker’s brilliant comic creation.

The former prison at Oxford – in what remains of William the Conqueror’s castle complex – has been converted into a stylish hotel with 94 rooms and suites.

Our room – in the former A Wing – was once not one, nor even two, but three cells.

As we stepped out of the lift on the fifth floor, the galleried landings – linked by iron staircases with whitewashed walls inside a giant glass-roofed atrium – looked familiar enough from countless TV shows and films.

It was easy to imagine Fletch, Godber, Grouty, Bunny and Blanco and the rest playing cards and table tennis down below; the bark of Mister McKay echoing round the spectacularly refurbished interior.

Not surprisingly, it has been used as a backdrop in Inspector Morse, along with Bad Girls and The Bill. Movies including 102 Dalmatians, The Spy Game and Lucky Break have been shot here – and, most famously of all, the original Italian Job, with Michael Caine and Noel Coward.

It must have been a bleak, forbidding place when it was stuffed with cons and screws – but now it’s a beautiful building on an epic scale, and a wonderfully unusual short break destination.

The brasserie restaurant, in the old keepers’ quarters, is where workmen found the remains of dozens of executed prisoners fairly recently (the prison was in use until 1996) – but don’t let that put you off your fine dining experience.

There’s an original cell to look around. It’s interesting to note than Victorian convicts would have a whole room to themselves, but by the mid-20th century prisoners were crammed in three to a cell … that’s progress, I suppose.

Step outside (a privilege not afforded to previous inmates) and you’re at the heart of one of the world’s finest cities, famous for its dreaming spires, and just perfect for exploring on foot. And, for added value, many of the best attractions are free, such as ...

• The Ashmolean, the world’s oldest public museum (established 1683), recently reopened by the Queen following a £61m refurbishment and expansion. Its exhibits range from the Stone Age, through Ancient Egypt, Greece and Rome to paintings, sculptures and textiles from China, India, Japan and Tibet, plus a superb collection of British and European art. If you’re quick, you can still catch the pre-Raphaelite exhibition, which runs until December 5.

• The Museum of the History of Science, housing an unrivalled collection of over 10,000 objects in the world’s first public purpose-built museum building, the Old Ashmolean, on Broad Street. Exhibits include Einstein’s blackboard and cameras that once belonged to Lawrence of Arabia and Charles Dodgson, formerly a maths tutor at Christ Church, also known as Lewis Carroll, author of Alice’s Adventures in Wonderland.

• Pitt Rivers Museum, a “mad granny’s attic” of over a million artefacts. Display cases are stuffed with amulets, beads, pots, tools and weapons, while masks peer from behind high walls and boats sail overhead. Many exhibits still bear labels hand-written by the original curator.

Everywhere you look in Oxford are stunning structures, such as Christopher Wren’s Tom Tower, over the entrance to Christ Church (where the cavernous dining hall was the inspiration for Harry Potter’s Hogwarts), and Radcliffe Camera, the earliest example in England of a circular library… which, sadly, isn’t open to the public.

The old prison, of course, also contains many secrets within its thick walls. Before we checked out, a hearty breakfast set us up for the day ahead. And guess what was on the menu? That’s right… porridge.