Sales of the denim trousers, a wardrobe essential for much of the 1980s and 1990s, took a dive in 1997 because middle-aged wearers such as the television presenter Clarkson made them seem unhip. But, thanks to their return to the catwalk, in the past 12 months UK sales of jeans have risen and there has been a dramatic increase in the number of women wearing denim.