Observations: Annie Kevans - There's more to these faces than meets the eye

Annie Kevans has an eye for what makes an eye-catching portrait. Her oil-on-paper likenesses look simple, almost childlike, but they come with a sting in the tail. The 36-year-old artist began painting in her final year at St Martin's with Boys, a set of pictures of dictators as children – a blue-eyed Hitler in a simple brown jacket, a wan Franco, a petulant Pol Pot. "People think it's a bit naff, really cutesy and then, oof, it's Hitler."

They are portraits only in a loose sense. "I paint people," she corrects, her works being a composite of existing images, research and imagination. Having spent months looking for snapshots of infant autocrats at play, she eventually gave up. "I thought, 'Does it matter anyway if I make them up?' It caused quite a lot of debate." And interest, too: Charles Saatchi snapped up the degree show in its entirety.

Since then, she's painted Girls, a series of ruby-lipped, sexualised images of child starlets such as Shirley Temple, Brooke Shields and Britney Spears. And at the art fair Volta in Basel this summer, she presented All the Presidents' Girls, a record of Presidential mistresses from the 18th century up to the present day, running the gamut from the obvious (Monica Lewinsky, Marilyn Monroe) to lesser-known scandals such as Sally Hemings, the 15-year-old slave and maid to Thomas Jefferson's daughter, who became pregnant with the President's child. The works sound sensationalist, but Kevans' use of thinned oil paints on canvas paper gives her subjects a melancholic, dreamlike feel – all eerie wide eyes, drippy hair and smeary lips.

Now, in Ship of Fools she's turning to mental illness with portraits of successful men and women who have been dogged by depression, eating disorders, addiction and other troubles. Michael Jackson, Winston Churchill, Mark Twain, Drew Barrymore and Princess Diana all feature, alongside the tortured artists Van Gogh, Jackson Pollock and Georgia O'Keeffe. "I've always been interested in madness – there's a lot of it in my family," says Kevans, who was inspired by medieval images of European towns shipping their deranged inhabitants out to sea. "God, can you imagine all the greats with mental illnesses on a boat together?"

Last night's private view was held on board the Golden Hinde. It was the first-ever exhibition to be staged on the reconstructed Tudor warship, which is docked within site of Tate Modern. "It's quite small, dark and miserable inside, which really brings the theme home," says Kevans.

Ship of Fools opens today and continues until 23 December in FAS on New Bond Street, London W1

www.faslondon.com; www.anniekevans.com