He’s Boris Johnson’s father, a well-respected conservationist and a mountain climber. We manage to catch him at home

Stanley Johnson may be wearing his jumper inside out but he’s a consummate professional.

He’s 71 and counts in his recent personal achievements the fact that, in the last two years, he’s not only continued to be a heavily respected voice on the environment but also climbed two mountains.

It was easy, he says, sat in his Regent’s Park living room, laden with pictures of all of his blonde offspring (including a young Boris) and the mandatory copy of The Telegraph on the footrest. “When it occurred to me to climb Mount Kilimanjaro, I thought I’d better walk up Primrose Hill, which I did, about once, and that seemed to me to be fine. Walking up Primrose Hill was a perfectly adequate training for climbing Mount Kilimanjaro.”

Seventy-one is a good old age to be gracing high altitudes. But Johnson Snr took it all in his stride, it seems. “It was all absolutely fine, absolutely fine. Coming down you have to do a long haul and that is a bit wearing on the feet.”

“A couple of months later, I thought, well, what other mountains begin with K? And one which came to mind was Mount Kinabalu, which is the highest mountain in Southeast Asia. I think I flew to… oh, my mind’s drawn a blank. I flew to Borneo, but what was the place? I’d have to read the book. I can’t believe this, does your mind ever go blank?”

Johnson consults his most recent book, Where The Wild Things Were, a volume that draws together his journalistic work on conservation topics, from 2006 onwards, including the two mountains and many other adventurous yarns.

It’s pretty surprising that he is at home, actually. Looking at the book, he has spent most of the last seven years zipping around the world, sending dispatches back to national features desks about gorilla populations (he is a trustee of The Gorilla Organization, based in Primrose Hill), rainforests and all sorts of other things. That began after a career in politics (Johnson was a Conservative MEP from 1979 to 1984).He also ran, unsuccessfully, as a prospective MP for Teignbridge in 2005. He’s just finished another book – on the UN, which will be number 26 when it is published. Johnson is a busy man.

His books range from the autobiographical Stanley, I Presume, to fiction made into film (The Commissioner) and a great swathe of works on population – something that, as an environmentalist, he has been talking about since 1970. “I’ve written five books about population, they all have population in the title.” He lists them all. “So yes, you could say that population is the most important issue with regards to the environment.”

“I was on the Sky newspaper review the other day and I was talking about this wonderful woman Melinda Gates, who is married to Bill Gates and has decided to give half a million pounds to help women in Third World who don’t have proper access to family planning. There are at least 120 million women who don’t have proper access to family planning and thousands of women each day who die of childbirth-related complications and quite often the baby dies as well.

“Population is a root cause of problems. And then the other root cause is not just the numbers, but what we do nowadays.” He looks at the cup of tea in his hand and laughs. “At least it’s not a lobster.”

He begins telling me about how he was at the last environmental conference in Rio and had to chair a meeting about cities. “With cities you can make a huge difference. In a country like the UK, probably about 80 per cent live in a city. So with buildings you can make a difference with double glazing and the like.” He looks around again. “I don’t think the Crown estate will allow that.”

He admits that, as an environmentalist, he will have to “slim down” his lifestyle. As the head of the Johnson clan, he’s an automatic cyclist. He’s cycled for 50 years and hopes that is good for the environment. Still, he has a complaint to register with the Mayor. “Much as I approve of the efforts that are being made in London on cycling, I’m sure we could go much, much, further than that. I find it such an easy way of getting around. I don’t know why more people don’t do it. I think there is a bit of a hostility now between cyclists and motorists.” Boris has done well with his bikes no? “What? Bikes? Oh yes, yes.”

His jet-setting may also have to be curbed, which will be helped by the fact that, as he turns 72 in August, his mountaineering days might be behind him. “I don’t think I am going to do another, I don’t know. The trouble is that the other mountains which begin with K, Kanchenchunga and then there’s K2. I think you are talking about serious mountaineering once you get into the higher reaches of the Ks.”

I wouldn’t put it past him.

Where The Wild Things Were is published by Stacey International priced �8.99.