My son gazed at the kitchen dresser, silently counting the rows and rows of colourful mugs adorning the shelves. “Do you know?” he said finally. “We could invite 100 people to tea and not have to borrow any cups.”

Most of the cups are from Emma Bridgewater, the eponymous potter whose china adorns kitchens the length and breadth of  the country. Manufactured in Stoke-on-Trent and sold all over the world, Emma’s china is decorated with everything from those famous multi-coloured polka dots to flowers, birds and Union Jacks. My own favourite, produced in the nineties, is a cup printed with purple houses, keys, hearts and stars. It’s been used so much that it’s got a hairline crack down the side but I can’t bear to throw it away.

This week Emma Bridgewater celebrates its 25th birthday. The company has produced a limited edition silver baby mug, is holding a fanfare of celebratory events and Emma herself has appeared on Woman’s Hour and Sky News.

I first interviewed Emma and her husband Matthew Rice back in the early days, when they lived in a house on the Fulham Road crammed with old china, architectural drawings and assorted animals – both live and stuffed. A quarter of a century on, their company employs more than 100 people in Stoke-on-Trent and is the only large manufacturer that makes all its pottery in England.

It’s a huge success story, which started in 1985 when Emma was looking for a cup and saucer as a birthday present for her mother but couldn’t find anything she liked. Even though she didn’t have any formal art training, she hit on the idea of producing her own designs.

“I knew before I started my business that it was going to take off,” Emma told me back in 1990. “If you’re going to do something successfully, you have to believe in it 100 per cent. It’s never an accident. You’ve got to wake up every morning with a powerful conviction of what’s going to happen today, what it is you’re trying to achieve.

“Mind you,” she added, “there were days when I got up with no conviction at all and went straight back to bed with a novel.”