Don't touch the barometre]: Magnus Mills finds strange rules and an occult glow on his visit to a lighthouse

I LAY in my sleeping bag listening to the foghorn. I had no choice as it was a very big foghorn and not far away. In between the blasts I could hear the surge of waves against the cliffs below. As soon as it was daylight, I thought, I would get up and go down for breakfast.

So I waited, and waited, while the room resonated every 60 seconds. There was no clock in the room, but I kept thinking that surely it should be light by now. And suddenly I remembered: they had put me in a room without windows.

I was staying in a lighthouse on the west coast of Britain, where my long-lost mate Barry is an assistant lighthouse keeper. There were so many other assistant keepers there that there was no room for me in the sleeping quarters, so I had spent the night in the room by the foghorn. I got up and opened the door. Outside it was broad daylight, or foglight, or whatever you call it when visibility is down to a few feet.

Barry had been up for hours but had considerately waited for me to surface until he prepared breakfast. Anyone who thinks lighthouse keepers live a lonely life and get a decent meal only on Christmas Day ought to see this lot cooking breakfast. Up to six of them look after the place and they make sure they take plenty of food with them. And as this is a 'shore station' - one on the mainland - the keepers can easily go foraging for more. There is even a daily delivery by the milkman.

Barry is a veteran of the picture-book 'tower' lighthouses, usually to be found on rocky outcrops - notable examples are Bishop Rock, off the Isles of Scilly, the Wolf, which lies south of Land's End, and the Needles, on the Isle of Wight - where each keeper has to work out exactly how much food he will require for the duration of his duty, and is accordingly allocated space in the supply helicopter. No milkman there.

Barry has also been on 'island lights' such as the Skerries, off Anglesey. He likes the islands best, but the shore station made my long-awaited visit easier. His spell of duty was just coming to an end when I arrived, so he had a couple of days to show me round. The previous morning I had been in Brixton; by midafternoon we were thrashing along the wild coastline of Wales, dodging waves, with the January wind tearing at our hair.

Barry wanted to show me the lighthouse control room, but first he had to obtain permission from the principal keeper. 'He's a bit of an ogre,' he confided. Permission was granted for an evening visit. The principal keeper was there, surrounded by all the stuff you would expect to find in the control room of a lighthouse, such as binoculars, plus all sorts of humming electronic equipment I would not have thought of. And on the wall was a barometer. I walked over and gave it a tap. The noise Barry made was like a strangled bark: 'Don't touch it]'

I leapt back, startled. 'I always thought you were supposed to tap them,' I said, meekly.

'Not in a lighthouse, you don't,' said Barry, who has to take a reading from the barometer every day and chalk it up outside the lighthouse. Apparently, if you tap a barometer, you run the risk of damaging the spring.

The principal keeper stood in silence by the window. Then in a low voice he spoke: 'You had better show him the light.' Barry led me through a narrow door and up a winding staircase. 'Don't touch the handrail either, added the PK, 'I've only just polished it.'

I obeyed, and climbed the stairs walking sideways. The brass gleamed. Handrails in lighthouses are not to be touched, just polished. And there at the top was the enormous lamp, flashing on to the sea.

Barry began talking: 'Now this is what we call an occulting lens. It can be seen 14 or 15 miles away, but it does not revolve. It is called an occulting lens because it reduces the light to a glimmer, instead of going on and off completely, which would cause the filament to fail . . . etc, etc.'

Barry had evidently shown people round before. I listened vaguely. I watched the light occulting. I watched the oil tankers rolling by. I watched the lightship out at sea flashing as if in response to another automatic light somewhere along the coast. I wondered what a 'watch' in the dead of night was actually like.

A lonely visit? A time to reflect? Ha. When we returned to the control room the principal keeper was watching the television. What do lighthouse keepers do in their spare time? Well, Barry is quite a good painter and illustrator, especially of wildlife and marine subjects, as he has plenty of opportunities to work on commissions. And then there's the pub. He throws a nice dart, does Barry.

But he had just become a father, so he was looking forward to his leave. We were travelling back together the following day. He had been polishing his Morris Traveller in readiness. As I approached the kitchen I heard him say: 'Well, home tomorrow.' I asked him who he was talking to. 'I was talking to myself,' he replied. Maybe it was time he had a break.