Author and father of three Conn Iggulden is exactly the kind of dad I had always wanted to be to my son: a Superdad. He knows how to build a treehouse, make invisible ink and crack the mysteries of Morse code. He can teach a boy to read the stars and, most important of all, teach a boy how to reach for the heavens.

And now I can, too. For these and many more of Iggulden’s skills are revealed in his book, The Dangerous Book For Boys. It’s at number one on the non-fiction bestseller list and has sold more than 520,000 copies. And his historical novel on the life of Genghis Khan — Wolf of the Plains — has just taken the number one position on the fiction bestseller list. Iggulden’s double number one is a record that has never been achieved before by a British author.

“When I heard the news I was stunned, absolutely amazed,” he says.

It’s fitting that Iggulden, 35, should be the one to break this record — his books are all about having a go, taking a risk, never giving up. He loves tales of plucky Englishmen such as Douglas Bader and Scott of the Antarctic who refused to quit, stayed the course — which was what he did after he left his job as an English teacher in 2001 to become a writer and found nothing but rejection: “I have a whole attic full of failed manuscripts. But I just stuck at it and kept writing. It’s all I ever wanted to do.”

Some might think that a man such as Iggulden, who has written four big novels on Julius Caesar, is working on a series of novels about Genghis Khan and is planning to write another non-fiction book on the great heroes of history, is having some serious masculinity issues.

Actually, he hasn’t. In person he is polite and unassuming, with a touch of self-deprecation. He believes that it’s our society that has the problem with masculinity. “We won’t let boys be boys,” he tells me. “It’s important that we preserve a kind of childhood that seems to be disappearing.”

So why has the book — which is so radically un-PC that it includes how to shoot and skin a rabbit and celebration of the British empire — become so successful? Iggulden has his own theory: “I think the book’s success is in part a reaction to the whole health and safety culture that constricts the freedom of our kids. Parents are constantly trying to protect them from this or that. But being an adult is about learning how to handle risk. This is what we learn when we’re young. We’re going to create a generation of frightened men.”

“So are you saying that we need to expose our children to more danger?” I ask.

He laughs nervously: “Yes, I know it sounds terrible when you say it like that, but it’s true.”

Iggulden, who has been married for 10 years, lives in Hertfordshire with his wife and has a six-year old boy and two girls aged one and three. Doesn’t he ever worry about his son getting into trouble? He squirms in his seat: “I’m a parent, so I know this fear. I remember running around with my son in a field and he suddenly disappeared out of sight, and I remember standing there sweating and thinking, God, should I run after him? But I made myself stand still. I didn’t want to nanny him.”

What, I wondered, has happened to the kind of free and open childhood that we once had in this country? Or maybe it’s become something of a nostalgic myth? Iggulden is convinced that it’s no myth and cites as an example his own childhood. He talks about growing up in deepest suburbia, in Eastcote, Middlesex, in the 1970s as if it were magical, a lost kingdom. “It was a time when everything was interesting and anything was possible,” he tells me. “I wasn’t a maths geek or a science geek but I was very curious and always fascinated to find out how things work.”

So while other kids were watching Top of the Pops and going to the local disco, Iggulden was learning how to make his own incendiary bombs and “going off and getting up to mischief”. He admits that he was a “disaster” when it came to discovering “the mysteries of girls”, but when it came to the mysteries of “how to make my own spud gun or open all the doors of a Tube train” he knew everything.

Where did he get his inspiration and fascination for discovery? What Iggulden had were two inspiring parents: “My dad was an ex-bomber command in the second world war who became a teacher of physics, maths and woodwork. He loved to recite poetry and tell a cracking good tale. Mum taught English and history and we got from her a sense of history as an exciting series of stories.”