Middle age is getting harder to define these days what with 56 - year-olds like Paul McCartney's wife Nancy Shevell looking amazing in bikinis, but now the big giveaway, the cast-iron proof that you are old enough to have bunions and grey hairs and the beginnings of regular digestive problems, is the onset of Midorexia. A Midorexic is someone who, when they turn 50, is quite likely to rush out and buy their first ever pair of leather trousers (or in my case Terry de Havilland gold snake platforms) without considering why they've never worn leather trousers at any time in the previous decades.Midorexia is the belief that not only can you be attractive forever (a good thing) but that you are actually MORE attractive now than you have ever been and it would be criminal not to take full advantage of that fact before it's too late.This conviction that you are enjoying a late burst of gorgeousness is something both men and women are equally prone to. I'm talking about that friend of yours (mother of four under 25) who has recently taken to wearing a denim mini skirt and the other one who has got those bottom-enhancing Levis.Those in the grip of Midorexia think their late onset gorgeousness has roughly double the impact of gorgeousness in people half their age. They think they look amazing - in the dungarees or the plaits or the thigh boots - not because they do but because they wouldn't have dared go near them 20 years ago. This is not denial. Denial is Donald Trump's candyfloss comb-over. This is more like temporary blindness, like self-love gone rogue.It's no one's fault. It's to do with better hair dye and better diet and A-listers working around the clock to defy natural law while pretending they're just living healthy, fulfilling lives. But mainly it's a potent combination of blind refusal to give any ground (So young people go to festivals... We can do that! So skinny jeans are in, we can do that! And those clogs! We can do that!) and some strange hormonal surge comparable to the adrenalin rush you get when trying to get back into a boat in a strong current.You're probably thinking: What? But I hate my neck. I loathe how I look in shorts. I have abandoned bikinis and I'm seriously considering getting one of those bowl cuts that you never have to bother about, because no one looks at me, anyway. Yes, yes. But that's because you don't have Midorexia, lucky for you and especially lucky for your loved ones. Others have it badly (see Gwyneth Paltrow whose MX is so bad she is happy to tell the world that among her girlfriends the talk is all about her pert bum: "You know this isn't so bad for 40, right?" And [my friend] goes 'It's not so bad for a 22-year-old stripper!'")Paltrow's obsession with her behind is textbook Midorexia. However, while most of us aren't doing those cut-away Brazilian bikini bottoms, some of us are behaving equally oddly given our circumstances. Closer to home I am aware - thanks to some last-minute interventions from my husband and stepsons - that Midorexia can strike even when you think you're being vigilant and you've thrown out everything that's borderline mutton.We have an unspoken system in our house now: I stand at the top of the stairs (wearing, say, my new jumpsuit), younger stepson says: "Wow" (meaning don't come any further whatever you do), older stepson looks at his father, father looks down. It's foolproof. ..