Before your skin disappears under layers of tights, woollens, gloves and coats not to be seen again in public until next spring, take a moment to look at your moles. Summer in London may have been a wash-out but tanning on foreign holidays or sun beds means skin cancer is the country's most common cancer, with 100,000 cases annually. Overall the disease kills 2,000 people a year, and rates are predicted to rise.