A new BBC series sees polar explorer Sir Ranulph Fiennes, solo yachtsman Sir Robin Knox-Johnston and BBC World Affairs Editor John Simpson put each other to the test - in Afghanistan, the Arctic and the stormy seas off Cape Horn. Here the 3 describe the experience of making the programmes.
Sir Robin Knox Johnson "To prepare us for the trip to Afghanistan with John, we had to do the BBC's Hostile Environment course down in Surrey . The most memorable part was being "kidnapped" - the tutors were so focused on kidnapping Sir Ranulph, that they let me get away. I managed to escape and only returned once the exercise was well and truly over!
Robin Knox Johnston - "The trip to Afghanistan with John was fascinating. We flew to Kabul and then travelled on to Jalalabad and the badlands near Tora Bora on the trail of Bin Laden. It's so interesting to see a country you've read and heard so much about for yourself - the people are very impressive.
The main aim was to watch John in his work as a journalist. John's depth of knowledge - of the area and of what's going on there - is remarkable. And he has a very interesting attitude to danger - he's so focused on the job he doesn't see danger in the same way as other people.
Sir Ranulph Fiennes "We all got on extremely well, right from the start. I'd met Ran (Ranulph Fiennes) before, but not John. The advantage of working with people with lots of experience is that you're not all fighting to be the boss. It's not like being in a group of 22-year-olds. You're older, wiser and respect each others' abilities, so there was never any question about who was in charge."
Ranulph Fiennes - "Afghanistan was the most interesting and fascinating - I enjoyed being able to go with someone who really knew the background.
If you want to learn about the place, the best person to go with is John Simpson - I wouldn't have missed it for anything. The Khyber Pass was lovely stuff - it's such a shame for the world's tourists that they can't go. Similarly with the Swat Valley, because of its troubles.
I had doubts about going around Cape Horn, having previously experienced terrible seasickness. I wouldn't have gone if it wasn't for the fact that I was told that in the 21st Century things had changed - that there were now patches you could get to deal with this sort of thing. It turned out to be a load of garbage. Although I didn't enjoy it, it was nice to go with Robin, with all his experience.
Before we went, we had to do a hostile environment course in Wokingham. No offence, but Wokingham is a really boring place. The hostile environment course wasn't boring, though. It reminded me of a special forces interrogation course 40 years ago.
After watching John, would I like to be a journalist? No, there are too many tight deadlines."
John Simpson "I knew it was going to work from the moment I rang the other two out of the blue to ask if they would join me on the three expeditions. There was no hesitation with either of them, and they both used the same expression: 'It sounds like fun.'
It was. Difficult, certainly, sometimes dangerous and often daunting, but always enjoyable. Even when we heard that the Taleban was organising an ambush for us on our way back from the Tora Bora Caves. Even when the waves got up as high as my house when we entered the southern ocean on our way to Cape Horn in our 48-foot boat. Even when I sat in our tent out in the Arctic wastes of northern Canada and realised that I'd got a nasty case of frostbite.
Sir Robin Knox-Johnston, the most famous sailor in the world, was 69; Sir Ranulph Fiennes, the world's greatest living explorer, was 64; so was I. People always ask us when we plan to retire, and each of us answers, "Never."
What better way to prove it than by going to places that most 30-year-olds would think twice about?
There is a great deal of unconscious ageism in our society. A senior television executive said something about not wanting to see three old men wandering across the screen.
So we certainly did have something to prove.
The best thing about the series was that two of us were always outsiders. Ran Fiennes and Robin Knox-Johnston had never been to Afghanistan, and never been involved with a hard news report for television.
They watched as my usual news team and I compiled a report for the News at Ten. And knowing that they both have strong opinions about things, I encouraged them to challenge what I said, and the conclusions I reached. I found it really useful.
On the Cape Horn trip, it was Ran and I who were the outsiders. Neither of us had done any open-sea sailing before, especially not in waters that were so famously stormy. We didn't even know whether or not we would be seasick.
It was stressful for both of us - and Ran has had major heart-surgery, and a recent operation for cancer. The courage and determination of the man were quite extraordinary.
I don't suppose either of us will qualify as the year's most promising newcomer to sailing; but we got round the Horn successfully, and even landed on Cape Horn Island. Robin told us this meant that we were now eligible to wear a gold earring. Not quite our thing, somehow.
The hardest trip physically was man-hauling sledges across the deep-frozen Frobisher Bay in the far north of Canada. At one stage we had to pull 360 lb each - the equivalent of two full-grown men. Any thought I had had that it would be like hauling it over an ice-rink was quickly forgotten: the surface was more like a rocky desert.
Ran was so used to this kind of thing that he must have found our progress irritatingly slow, though he was too gentlemanly to show it.
Robin showed extraordinary physical strength. I could hear him roaring salty insults at his sledge.
I just kept my eyes on the ice in front of me and tried to think about other things. It was the most unpleasant exercise I have ever undergone, and it never seemed to stop.
The one superb thing was the landscape - when, that is, I raised my head to look at it. We were trekking in January, and the sun rose above the horizon for only a couple of hours a day. But the dawns and sunsets lasted for hours, and the colours on the ice were unforgettably wonderful.
It was extraordinarily cold: -39C when we set out, and when the wind was blowing at 30mph the temperature must have dropped as low as -50C.
We were told to go to the lavatory in our tent, hygiene being less important than frost-bite. But the thought of doing what ought to come naturally in a small tent in front of a baronet and a knight of the realm was too much for me.
I made my way out into the freezing cold - and although I only took my four pairs of gloves off for three minutes, that was enough.
The doctor ordered me out, and I was medivaced out. I missed the last day and night of the trek, and felt nothing but guilt.
All three trips, in their different ways, were life-changing. And in spite of everything the Taleban, the angry ocean and the bitter cold could do, we stayed the best of friends.
I would happily go back to Cape Horn. But I'll give the Arctic a miss in future."
This article was featured on the BBC website http://news.bbc.co.uk/1/hi/world/7966683.stm
Top Dogs: Adventures in War, Sea and Ice, a three-part series, airs at 2100 on BBC2 on 27 March, 3 April and 10 April.
Copyright Speakers Corner 2016