Don't blow your nose in Japan! You might upset the locals - or would you?

Years ago, I was dining in Oxford with a Japanese tourist when suddenly a guest on a neighbouring table let out an explosive, barked belch. My Japanese friend's eyes widened in astonishment. "Ahh," he murmured. "In Japan this is...not possible."

So no belching in Japan then. And before my trip to Tokyo last week, the other big thing that everybody assured me was "not possible" was nose- blowing in public.

From the Japanese point of view (know-all friends insisted), bodily effluents were bodily effluents, regardless of the orifice from which they emerged. Putting a snotty handkerchief into my pocket would be the equivalent of something quite unspeakable over on this side of the world.

But what if I caught a cold on the flight over to Tokyo? According to my latter-day cultural relativists, the correct behaviour in the circumstances would be to keep sniffing until I could reach the privacy of the nearest bathroom. Blowing my nose behind a locked door would not, apparently, be a problem.

In fact nose-blowing was not the only catastrophic faux pas that dumb tourists might commit in Japan. More serious still would be to traipse my muddy shoes around the inside of somebody's house, grubbying the tatami of my hosts. Worst of all, so I learnt, would be to jump into the communal bath without rinsing off my soap suds first. Of course, I had no intention of dirtying anybody's tatami or of fouling their bath-water. But I wonder how many people would really have minded if I had, say, given my nose just a tiny little blow?

The fact is that none of these supposedly immutable laws of behaviour are really as rigid as they seem. Look at the British, for example: according to Japanese guidebooks, it is extremely important for visitors to Britain to talk politely about the weather with the locals. But is it essential?

Sometimes we just get it wrong. We all know the experience of dressing up from head to toe in preparation for visiting Islamic countries, only to discover, on arrival, that the locals are actually wearing shorts and mini-skirts. In other cases, we cast political correctness to the wind and decide that our own customs are better. In China, it is normal to spit in public places, but I have never heard of any tourist in China deliberately taking up spitting specifically to put the locals at their ease. We congratulate those few Chinese who ape Western habits by refraining from spitting in our presence.

Lots of cases though are much more tricky. When I visited Iran, for example, I had been told on no account to attempt to shake hands with local women. The snag was that Iranian women had equally been told that they were on no account to refuse the proffered hands of Western tourists (who have a strict habit of shaking hands with everything and everyone they meet). The result was a cultural impasse, with me nervously withdrawing my hand as the ladies were nervously putting theirs out.

Iranians apeing the West? Quite the opposite. They were, in fact, asserting their cultural independence by showing me that they knew as much about me as I did about them. And this was all very alarming to my comfortable assumptions. After all, I was the one who was supposed to know about the locals, not the other way round. In contrast to sophisticated tourists, locals were supposed to be blissfully unaware of the possibility of cultural choice.

Basically, battle has been joined. There is a mortal struggle going on around the world between locals and tourists to get the better of each other. And one thing I learnt in Japan was that the Japanese, predictably, are racing ahead of the game. In upmarket hotels, for example, staff have been trained to respond differently to guests of different nationalities. To Japanese guests they bow and lower their eyes. To Americans they grin and catch the eye and exclaim, "How you doing?"

To passing Brits, for all I know, they are being trained to doff their caps and belch.