Has Posh got thinner? What's the latest on Britney? Who's getting together and who's splitting up? Every Tuesday, two million eager readers snatch up their brand-new copy of "Heat", ready to devour the latest gossip about the celebs. But there's one question everyone's desperate to know - what are the celebs really like? Who's got the craziest demands and the biggest entourage at a photo shoot? Do any of them eat normally? Who's nice, who's nasty, who's a demanding diva and who's just plain weird.One man has the answer. Mark Frith turned "Heat" into the biggest celebirty mag in the country. Cheeky, funny and never fawning, "Heat" was a new source of celeb info when it started in 2000. And Marks' been there since the beginning, from his first interview with Posh to the rise and fall of Jade and Big Brother, through to Britney's tragic descent from sexpot to being sectioned. From Kate Moss and Paris Hilton to Amy Winehouse and Cheryl Cole - in green rooms and VIP lounges, celebrities have confided in Mark and have been highly indiscreet in his presence. Now, for this first time, Mark is opening up his diaries. And no one is safe.