A strange thing happened on the way home the other night.

My friend Sarah, who was working on her laptop, noticed that its clock had stopped working.

It had been working when she got on the train at Victoria, but at some point between there and Haywards Heath, where we were when she looked at it to see if the train was running on time, it had stopped.

Which is unusual because the rest of the computer was functioning properly, the battery was fully charged and although neither of us know much about computers, beyond how to turn them on, there seemed no obvious reason for it to have stopped working.

"What time is it?" asked Sarah and I checked my watch.

"About 7.45," I said, after checking, while Sarah started trying to work out if there was any way she could get her computer clock going again and the train left Haywards Heath and carried on to Burgess Hill.

By Burgess Hill Sarah appeared to have found instructions which told her how to put the clock back on the right time and again asked me what time it was.

So I checked my watch and told her.

"About 7.45," I said, which, as she pointed out, was exactly the same time I had told her it was when she asked me at least five minutes earlier.

"That's strange," I said, checking my watch and then noticed that the second hand was no longer going round and it too appeared to have stopped.

I shook it and banged it a few times, the usual method for kick-starting any malfunctioning gadget (Sarah was using a more a patient and logical method with her computer), but to no avail. It had stopped.

"We must be in some sort of weird time warp," mused Sarah, wondering if this was just coincidence or something altogether more sinister.

She carried on tinkering with laptop and I gave up shaking watch and train carried on to Hassocks.

"It must be eight o'clock," I said to Sarah, knowing that the train usually stops at Hassocks at eight o'clock and since there had been no apparent delays or stoppages it seemed fairly safe to assume that it must be.

"What time does it say on your watch?" asked Sarah, to which I replied, "7.45," without looking. But she urged me to check it again. So I did and this time was surprised to find the second hand going round again and the time reading 7.55.

"It has started again," I told her, pleased that the shaking and banging routine had worked.

"So has the clock on my computer," she said.

By this time, the train was nearing Preston Park and the driver began speaking over the tannoy.

"I apologise for the delay to this service," he said. "It occurred somewhere between Gatwick Airport and Hassocks and I've no idea what caused it.

"The train was on time when we arrived at Gatwick. It's now ten minutes late and our arrival at Brighton will therefore be ten minutes late ... "

Sarah and I looked at each other and the driver continued. "As far as I'm concerned the train was running at the normal speed and there have been no stoppages for signals or anything else for that matter.

"I could give you an excuse which would explain the delay. I could tell you, for example, that we were held up slightly at Haywards Heath because somebody left a door open.

"But the truth is, I've no idea where that ten minutes could possibly have gone ... "