"The other snag about travelling in the jungle is that there are no passport controls when you move from one country to the next. I once crossed from Peru to Brazil on foot without getting stamped. I didn't worry at the time, because the Brazilian authorities were accommodating enough when I eventually reported to them. But a couple of years later I found myself in huge trouble when trying to re-enter Peru. When they typed in my name at immigration, the computer gave a big beep. It turned out that in Peru I was supposed to be dead. The area where I had been walking was a bit of a hot spot for drug-smuggling and was considered dangerous. They had launched some huge expensive army operation to look for me, and even had my guides arrested. Understandably everybody was pretty annoyed to find that, in fact, I was alive and well.
"On the subject of drug-smuggling, I once had quite an odd experience at Heathrow when stepping on to a flight to Bogota in Colombia. I had already been through passport control but suddenly there was this man in a dark suit taking me aside. "Why did I go to Colombia so often," he asked? "Because I'm an explorer," I told him. He told me to stop taking the mickey. "I've never heard of you," he said. It was a bit scary for a while, though he let me go in the end.
"Airports are always the worst places. When I was flying to Mongolia via Moscow, a friendly man at Heathrow had helped me get all my heavy camera equipment onto the plane. Trouble was, when I got to Moscow, they refused to reload my luggage for the connecting flight. I had already paid one official a $200 bribe, when another one came and demanded $500. I had to stoop to showing him my BBC card to stop him from getting my luggage down from the plane.
"Getting into Mongolia at that time had been amazingly difficult. When I applied for permission to do my programme at the embassy in London, they said: "We don't know. You go and find out yourself." What that meant was that I had to fly to Mongolia to get the paperwork done, then fly back to present it at the embassy.
"Anyway, Mongolia was pretty fascinating, if arduous. The toughest thing was losing all my pack animals - three horses and three camels - to a swarm of biting flies. They sucked all the beasts' blood out and laid maggots in their genitals, which swelled to the size of melons. I was devastated because we had already done a thousand miles together. But the locals couldn't understand why I was being so sentimental about mere animals. In fact they found the sight of me comforting my dying horse fascinatingly bizarre.
"One funny thing that happened to me in Mongolia was that the local equivalent to the KGB gave me the top-secret co-ordinates of their wells so I could find them in the desert. Anyway I trekked out for miles only to find that the wells were all padlocked. I started looking under nearby stones for the keys. No good. I had to completely retrace my steps."
Benedict Allen is an explorer, writer and broadcaster. His latest series, 'Edge of Blue Heaven', started on BBC2 last Thursday and will continue for the next five weeks.