How we met: Ben Carey & Henrik Delehag

'People miss the fact he's joking. We don't support al-Qa'ida or global warming'

Henrik Delehag is a 33-year-old writer and graphic designer. Born in Stockholm, Sweden, he came to Britain in 2000 and began working in advertising as an art director. He lives in west London and has a three-year-old son.

We met at an advertising agency. I was an art director and Ben was a writer. I thought he was brilliant. And we realised that we had the same outlook on pretty much everything. Soon, though, we found that our ideas were often a bit too extreme for what was expected of us at work. We were once given a brief to advertise Hula Hoops Shocks, a new kind of Hula Hoop with a really strong taste, and we made these films with electric eels coming out of toilets around Britain, which got banned from TV.

We decided our ideas needed to be ventilated elsewhere, and sat around at cafés all day trying to think what to do. Eventually, we came up with This Diary Will Change Your Life. We got a book deal in 2003 and left advertising.

Our first diary came out in 2004. It's now in its fourth year and gives disciples a life-changing task every week, ranging from proposing to a complete stranger, to joining an extremist organisation and out-extreming them. They've sold something like 350,000 copies worldwide.

We specialise in extreme self-help. Our new book for the American market is called Lose Weight! Get Laid! Find God! We've also written The Couple's Book, which helps lovers make the most of their relationship, from the first date to the divorce courts.

We have an office in Shoreditch. Ben arrives around 10am. I get in about 11am. I'm not a morning person. We tend to sit down and come up with concepts together. Then we split. I'm the visual person, while Ben writes. Sometimes we argue over concepts. We're both pig-headed. We refuse to make each other coffee. I don't know why. He can be very sadistic towards our fans. As part of a Diary task, a group of them once stalked him to his home. He was so grumpy with them that the next day on their blogs they likened it to meeting Saddam Hussein as he came out of his hole. They were drunk, though.

Ben has a very dry wit. Sometimes he's so deadpan that people miss the fact that he's joking. I always have to go around afterwards explaining that we don't actually support al-Qa'ida or global warming.

If we have a deadline for a book we pretty much work 24/7. We keep our social lives separate as we see so much of each other during the day. We haven't been on holiday together. God no. That would be too much.

Ben and I both see ourselves as outsiders. He sounds very English although in fact he's not at all. He went to an international school in Paris where all the English teachers hadn't gone home since the 1950s; they all spoke like Prince Charles. He keeps getting asked to drop the comedy accent.

Writer Ben Carey, 35, was born in New Zealand and grew up in Paris. He came to Britain in the mid 1990s and started working in advertising. He lives with his girlfriend in north London.

Henrik came over as an art director from Sweden, and at the time every self-respecting agency in London had to have a Swede. That was the trendy thing to do. Even by Swedish standards, Henrik was quite exotic. He started working with another writer and within three days this writer just disappeared off the face of the earth and no one has really heard from him since.

Then I was put together with him by the agency. On my first day, I turned up at 9am and sat in his office and he rolled in about 12, hungover, not knowing what the hell I was doing there.

Things picked up and we soon worked out we were on the same wavelength, and it turned out to be a completely different wavelength to everyone else. That's what made us leave advertising and start Benrik. It's a meeting of slightly warped minds; I've not really had that kind of connection with anyone else I've worked with. The downside is that if one of us gets run over by a bus, because of the name, we can only hire someone else called Ben or Henrik, which would narrow the field down a bit.

Our books are largely humorous. Humour is a very distinctive thing. I think English humour, in particular, is very ironic and cynical a lot of the time. Benrik's humour tries to be slightly more positive - a bit more of a naïve anarchism.

Like most writers, I probably approach our work from a more intellectual point of view. And, like a lot of designers, he has more of a gut instinct about things. I think our working life is a laugh compared to most people's. He does, however, have a very disgusting personal habit, which is common to members of his country: snus. It's a rolled-up ball of tobacco which you stick under your upper lip to marinate. I think it's illegal in this country, but they all import it on the Swedish black market. Basically, it's a drug and if he runs out, our life becomes hell and all our ideas are judged to be rubbish. Inversely, when the snus turns up, everything goes smoothly again. It's like a Swedish crack cocaine.

Benrik isn't just a nine-to-five job; we're trying to run a cult here. It's very involving and you think about it constantly. Inevitably, when you're working in such close proximity you rub each other up the wrong way occasionally. Compared to Henrik I'm probably more of a stickler for punctuality. He doesn't have a body clock. He doesn't know the day of the week, which is profoundly annoying when you're trying to have an intensive working schedule going on. Of the two of us, people tend to assume he's the more obviously psychotic.