Considerably more than 39 steps

295 more to be precise - a total of 334 from the ground up to the bells.

Guess where we went today?

Anyway, Robert Powell got it completely wrong. 334 steps, as I say, and the filigree on the clock faces is 3" thick wrought iron. You really wouldn't be smashing through it in a hurry.

You probably wouldn't even have the breath to try. Our guide at least gave us breaks on the way up. The first was about halfway up - the level at the bottom of the photo here - which contains the Prison Room, where the Serjeant at Arms can retain recalcitrant Parliamentarians if necessary. Last used in 1880 when the atheist Charles Bradlaugh MP refused to swear his allegiance to Queen Victoria on the Bible.

The Prison Room is Room 1. Just as we were setting off up the steps the guide thrust a bunch of keys at the first of our group (my mother), said "Room 1," pointed upwards and disappeared into a sideroom. So we all trooped up the stairs with my mother holding the keys to locked rooms in an actual palace. Security, eh? "You're a general's wife," I pointed out. "You were born to this."

Photos are forbidden inside so I'd better get it down from memory, helped by the pamphlet they handed out. I'm not quite sure what I was expecting at the top, but I think it involved a vast chamber with a mass of clockwork in the middle and the four translucent clock faces all around. In fact the mechanism is in a small room at the centre of the tower and you get to the faces by going into a narrow grey-painted gallery the next level down. Behind each face is a bank of very large low energy light bulbs, but the rungs are still there from the time when the clock was gas-lit and someone had to climb up and light each lamp with a match.

The mechanism is either impressively big or surprisingly small, depending which way you look at it. It would never be used in a movie because it takes up too little space - but there again, it's 15 feet long and about 5 wide, which in practical terms is large. It has all the requisite cogs and wires that you'd expect and it's clockwork. Clockwork! After 150 years, it still uses the original mechanism of weights and pendulum (4m long) which dangle down the central shaft of the tower. The only concession to modern times is that there is now a motor to wind it up again. It's kept accurate to half a second a day - the speed of the pendulum is regulated by adding or subtracting old pre-decimal 1p coins. Add 1 penny and the clock gains 2/5 of a second in 24 hours. At one end of the chassis are four little levers, about a foot long, connecting to cables which disappear into the ceiling above. These ring the quarter hour chimes just like a music box - a wheel turns, teeth on it strike the levers in a set sequence, the bells chime.

The tune is adapted - loosely, I would say - from "I know that my redeemer liveth". Didn't know that, did you? There's even, officially, words to it: "All through this hour / Lord be my guide / and by thy power / no foot shall slide."

From the clock room it's up the final 101 steps to the bell chamber, home of Big Ben itself, which is level with the top of the faces and open to the elements (but grilled against pigeons). There are no more levels to climb after that - the whole of the roof space is one big chamber, but full of iron girders and gantries. We were there for the 11 o'clock chimes. Ear plugs were handed out but even so ... wow! You don't just hear the chime, you feel it - the main bong, and a whole range of harmonics that vibrate in your ribs and your teeth and the back of your head and last much longer than the chime does. Big Ben was originally hauled up the central shaft which was then sealed off so they could put the mechanism below it - so they're in trouble if it breaks. It cracked soon after installation so they simply reduced the weight of the clapper, turned it 90 degrees so the clapper would hit a different bit of the bell and crossed their fingers. 150 years later it's still going strong.

I've been to the Tower, I've been on the Eye, I've been inside the Dome, I've been to Westminster Abbey and all the cathedrals, I've even been to the Palace on a couple of occasions ... but I now truly feel I have Done London.

An interesting little coda to the day was chatting to a very friendly, pleasant young man with Down's Syndrome on the Tube. First he complimented my lovely wife on her hair, then got on to asking what sights we had seen, had we been in the Queen's house (he had), had we met any royals (he had; Princess Anne, rosette for Riding for the Disabled, 1983), did we know why Bond Street was called Bond Street (neither did he) ... A fairly surreal conversation, finally topped with:

"Have you met Una Stubbs?"
"No."
(Wistfully) "I would love to meet Una Stubbs ..."
???

Then he got off at Green Park.