Big Ben's safe pair of hands

John Tricki: "It's a privilege to look after Big Ben"

Thwaites and Reed, the company that maintains Big Ben is up for sale. Here, clockmaker John Tricki explains what's involved in keeping the famous timepiece ticking over.

In all my dealings with Big Ben, I've never known it to be faster than three seconds or slower than three seconds.

It behaves itself. It's amazing really, considering the size of it and the age of it.

All eyes on Big Ben come midnight, New Year's Eve

But then, we're up there every day and [we] wind it three times a week. And we're on 24-hour call should something go wrong.

New Year's Eve is always special. It's nice when I come down and am making my way home through the crowds. Everyone's smiling and shouting: "Happy New Year!" and I've been up there making sure it is.

On Millennium Eve last year, Big Ben was really spot on. The clock went 'boing' right on the millisecond of midnight.

It was smashing - we were right up the top of the tower with a bottle of champagne and some sandwiches when all the fireworks went off.

Trouble with the weather

Last night, we were both up there from about 8pm to make sure the timekeeping was spot-on come midnight.

Big Ben

Four faces with 312 panes of glass each

Numerals 500cm high

Copper minute hands

Gunmetal hour hands

If it's a bit slow or fast, you can move the weights, which include an old penny piece, along the pendulum to alter the speed fractionally.

Or you can stop the mechanism for a couple of seconds, timing it on your own watch.

We prefer to use digital watches because the time is right to the exact second. Before going up the tower, we synchronise our watches with the speaking clock.

Snow blanketed central London last week

During the cold snap last week, one of us went up each day to check that all was well.

If frozen snow had got on the hands, it would have made them too heavy for the mechanism to drive.

I've never known weather to stop a clock, but it probably could stop Big Ben because of the length and the weight of the hands.

Arduous job

We wind the time mechanism by hand, but a motor drives the strike and chime barrels.

People look at me with disbelief when I tell them what I do

There'd be no thank you from me if those were still done by hand - up until the 1920s, it took two men five hours to do it.

The mechanism is so highly geared that on the quarter chime, they would have been able to see what they'd wound up rolling off - it must have seemed like a never-ending job.

The time mechanism takes about half-an-hour to wind, with a little break to watch the quarter chime. That can be quite dangerous if you get too close to it - the big locking arms go spinning around. If you got caught in it, apart from damaging yourself, you'd probably damage the clock.

Job in a million

It's a privilege to look after Big Ben - and it's nice to be able to say that.

People look at me with disbelief when I tell them what I do. Few people outside the business realise what goes on behind that dial.

"Oh, that must be a marvellous job," they say to me. It is, but I just play it down.