AT THE age of 13, I made my first, utterly illicit, purchase. It was a shiny black-and-gold plastic case that you could fit into the palm of your hand and it contained a spongy swab and three shades of greenish eyeshadow: sparkly avocado, mushy pea and eau-de-nil. None of them, it should go without saying, complemented either my mouse-grey school uniform or pubescent complexion. That hardly mattered. The pounds 3 transaction was a cosmetic rite of passage and, like so many other British girls, my longed-for transformation began with a visit to the No7 counter in Boots.

This Monday, No7 will be celebrating its 70th birthday. Since the high- street chemist launched its own brand of make-up in 1935 it has been re- invented eight times, and the latest changes include new packaging, logos and uniforms for the No7 assistants, while 60 per cent of products have been given completely new formulations.

"It's a really trusted and `local' brand," says No7 creative director Lisa Eldridge, "Everybody's got a story about it. I remember saving up for a No7 cleanser when I was 14. It was in a beautiful glass jar, and when I got out into the street, I dropped it and it smashed. I burst into tears." With the arrival of import upstarts like Stila and Hard Candy in the last decade, Boots no longer has a monopoly on teen-appeal. However, No7 remains, schoolgirl vamps will be pleased to note, a reliable source for the most effective and lengthening black mascara, Full Impact Mascara (pounds 10), which is worth blowing your pocket money on, even after all these years.