Checking in was only made more interesting by the fact that while in Zimbabwe we had bought the local edition of Trivial Pursuit, which the Zambian customs officials thought enormously interesting when they found it in our suitcase. When we explained what it was, they seemed to lose interest.

The expatriates we had met in Zimbabwe had thought that buying this was an extraordinary thing, as most of them had spent time attempting to import British copies of the game. What is a novelty in one place might not be a novelty somewhere else. One man's Meat is another man's Poisson.

After check-in, as we were obviously at an airport devoid of anything else likely to capture the attention, we went through to the departure lounge, which bore a striking resemblance to the transit lounge where we had been a week or so before. After a few minutes, I found that I was in conversation with a guard who looked familiar. He had never seen any South African money. Neither had we: we had not been to South Africa, just to Zimbabwe. Curiously enough, he had never seen any of their money either. I was sorry, I couldn't show him any: surely he must know how tight the currency regulations were. I can only assume that he must have been very new at the job.

As it turned out, currency regulations in Zambia are not as tight as we had been led to believe. We were not questioned about the money we were taking out, although I consider this to have been an oversight. I would certainly not recommend counting on it if you were thinking of trading currency unofficially.

We discovered at the last moment that foreign nationals must pay their departure tax in United States dollars. Fortunately, we had a hundred dollar bill with us, which we carried just in case, but this did leave us with an unacceptably large residue of kwacha. We couldn't get rid of them, as there was nothing to buy in the airport.

The X-ray machines in Lusaka may well have been the sort that does fog films, but we were destined not to find out because it wasn't fogging any films at all, or doing anything else. Therefore, our baggage was all checked by hand. This was probably unnecessary, but you can never be too careful.

The flight left on time, and the food was good. A great disappointment was noticing the large number of South African products on offer, which Zambia Airways were obliged to offer to make the airline credible. Coca-Cola, unobtainable in Zambia itself, was there, clearly labelled in English and Afrikaans.

While somewhere over northern Africa, the famous notice "if there is a doctor on board, could he please make himself known" was broadcast, for one of the passengers had been taken ill, presumably with something quite serious.

We arrived over London on time, and as we fastened our seat belts and looked at the no smoking signs, the airliner came lower and lower, until on our final descent we almost reached the ground. The runway lights were bright, and then quite suddenly the pilot put on full power as we climbed into the air again.

Sudden fog has reduced visibility at Heathrow, we were told. We circled for a few minutes and came in for a second attempt, which took exactly the same form. The lights suddenly became covered with cloud, and the aeroplane climbed into the air. We will circle for a while, and then try again. As it turned out, we didn't try again. Visibility reduced to zero, and we were diverted to Gatwick, where we landed with no problem at all.

We expected to get off and clear immigration there, but this was not to be. The sick man was taken away in an ambulance, but the rest of us, having first enthusiastically looked at timetables and maps to see how to get back home from Gatwick instead of Heathrow, soon realised that we would be waiting on the ground at Gatwick for a while.

We were fortunate, I suppose, considering one story I have heard. It might be true, or it might not, that on one occasion the whole of western Europe was fog-bound, and a flight from South Africa was diverted to Athens, from where the passengers were bussed to London. This seems a particularly nasty thing to happen. Bussing from Athens to London would surely be measured in days rather than hours.

Anyway, looking out of the window, it seemed that every available piece of tarmac in Gatwick had a wide-bodied jet parked on it. Presumably the authorities couldn't cope with processing all Heathrow's overnight flights as well as their own. At this time, Gatwick was overcrowded, because their new terminal was still under construction.

So we waited on the ground for about two hours, and then took the short flight to Heathrow. I believe that there are very few who have flown from Gatwick to Heathrow at all, and less still who have done it on a Zambia Airways DC-10. We know that the airliner's name is Nkwazi because Zambia has no other wide- bodied jets.

The arrivals board in Terminal 3 incongruously declared that our flight had come from Gatwick, a name that jarred against the more exotic names from which most of the others claimed to have come. Most of those had been at Gatwick too.