Kate at Cheltenham. (AP)

London, March 15: It was all going so well for Kate Middleton. This week she was ranked at number eight in Tatler’s annual Best Dressed List. In January she sparked off a race for a monochrome jersey dress from Topshop, after being snapped by hordes of paparazzi on her way to work.

Style commentators were beginning to acknowledge the growing status of Prince William’s gorgeously glossy girlfriend and licking their lips at the possibility of another royal style icon.

But dear, oh dear! What Katie did next! Appearing at the Cheltenham festival this week wearing a dreadfully dull chocolate-brown tweed jacket, deeply unflattering calf-length skirt and that Sloane staple, a blue shirt, she seemed to have aged several decades overnight.

Of course, it takes more than a dowdy suit to hide Kate’s natural beauty — her slender figure, pretty face and lustrous hair were still on show — but while on a number of occasions she has proved that she can look really stylish, she is rarely fashionable because no-one with even a passing interest in this season’s trends would be caught dead wearing granny tweed, an A-line skirt and kitten-heel knee-high suede boots.

To be fair, many visitors to the races were caught out by the weather this week. This time last year Kate was photographed at Cheltenham wearing a mink hat and a long tweed coat by the Fulham-based designer Katherine Hooker. If the weather this week was as icily crisp as last year, she might even have got away with her frumpy suit.

The Cheltenham festival is not like the glossy fashion parade of Royal Ascot — it’s smart and more understated and, in many ways, Kate’s sensible outfit was fitting for the occasion. But there are many more modern takes on the suit that won’t frighten the horses and that Kate should bear in mind for the future.

She has shown in the past how fabulous she can look in figure-hugging suits — the fitted cream jacket and tight black-and-cream pencil skirt that she wore to Rose Astor’s wedding last summer was a perfect example of how much better Kate looks in styles that compliment her shape. So why not invest in some curvy little suits from a British designer such as Vivienne Westwood? Kate would look stunning in one of Westwood’s hourglass jackets and pencil skirts.