How We Met: Cressida Cowell & Lauren Child

Cressida Cowell, 45, is an illustrator and children's author, best known for her series of novels starring Hiccup the Viking. The first novel in the series, 'How to Train Your Dragon', was recently turned into a blockbuster animation by DreamWorks. She lives in Hammersmith with her husband and three children

We were 16 when we first met and we'd both just moved to the same boarding school, Marlborough in Wiltshire. I remember first meeting Lauren in somebody's study, and I felt she was a kindred spirit from that instant. I remember she laughed at all my jokes, which is a very loveable decision to make.

We were both arty, creative people and that was a big connection. Lauren's father was the school's art teacher, and it had a fantastic art department – which was part of the reason I changed school. I remember both of us writing the beginnings of books both alone and with friends – I did this tongue-in-cheek romantic novel called Angora of the Shetland Isles – although interestingly we never did that sort of thing together. What I do remember is that we used talk to each other about children's books we liked: I introduced Lauren to Molesworth and she introduced me to Grimble.

Since then, we've always been close, and it's spooky how things have happened for us at the same time by sheer coincidence. After school, we took different paths: I read English at university, and was briefly in publishing. I spent a lot of time in my twenties feeling a bit left behind, and Lauren was also having difficulties. Then, we had our first books published in the same year – almost the same month, in fact. Also we started out writing picture books, and then both wrote a novel based on our picture-book character, and again published them in the same year.

Along with my sister, Lauren is my greatest confidante and our lives overlap in so many ways. For example, my daughter Maisie voiced Lola in the TV adaptation of Charlie and Lola. Lauren was trying to persuade [production company] Tiger Aspect to use a child's voice, rather than an adult voice actor, because she felt it would be more in the spirit of things. So she came round to my house with a Dictaphone, and recorded Maisie, who was four at the time. When they heard it, they realised Lauren was right.

That's also a great example of how Lauren sticks to her guns. Five years before her first Clarice Bean book, she took it to a publisher who said, "Yes, we like it, we want to publish it... but we want you to change everything about it." She said, "You know what? I don't want to change everything about my book to please you." I really admire that strength about her.

Lauren Child, 45, is an illustrator and children's author, whose works include the Clarice Bean novels and the Charlie and Lola picture books. Her latest Charlie and Lola adventure, 'Slightly Invisible', is available now from Orchard Books. She lives in Belsize Park, north London

I met Cressida early on [at Marlborough] at what they call girl's coffee. One of the things I liked immediately about her was that she wasn't competitive. I could tell that she was funny and clever, but it wasn't in a show-off way. I'd come from a school where people were quick to pigeonhole you and you were always scared of saying the wrong thing. But because Marlborough had this arty reputation, it had an intake of unusual people, and there was a freedom about the friendships I made there.

Often in the holidays, I remember I'd go and stay with Cress in London, which was always quite exciting, being a country mouse. I remember funny afternoons when we didn't have anything to do and we'd start playing Cluedo, and then end up decorating the board because we thought it looked boring. I also remember Cress as the person who introduced me to taramasalata.

I was going through my parents' attic a few weeks ago, and I found lots of funny notes that Cressida had passed me in class. I think we've always shared a similar sense of humour. But on a deeper level, we've both always been interested in the psychological side of things: I think it intrigues us why people are the way they are, or why children react as they do.

It's great to have a friend in the same industry, and she's always giving me great advice. Recently when I saw her I was getting really panicky about my new book, because it was the first one which had been trailed a long way in advance, and that raised the anticipation around it. The next day Cressida phoned me up, and said: "Don't listen to anybody." That was really nice, knowing that she had been thinking about [my situation] beyond that evening.

One of the great things about a long friendship like ours is that it makes you feel forever young. We were at a friend's house not so long ago, and we were chatting on the fire escape, and Cressida dropped something over the edge. I remember seeing her nip over the side to pick it up, despite there being a huge drop below. I wasn't expecting her to do that at all; it's the kind of thing that takes you back to being schoolgirls again.

'How to Train your Dragon' is available on DVD on 15 November. Green Drops and Moonsquirters: The Utterly Imaginative World of Lauren Child, is at the Discover Children's Story Centre (London E15, discover.org.uk) until April 2011