Jazz singer Cleo Laine does not like being a grandmother. "It makes me feel so old," she says. "I love the children, but I don't knit and cook for them. When people say to me: 'How wonderful, you're a grandmother', I just think: yuck." She has spent the past five decades touring the globe as a jazz singer and picked up a Grammy along the way - "It's in the toilet."

Cleo and John Dankworth have converted an old stable block in their back garden outside Milton Keynes into a jazz version of the opera house at Glyndebourne. A signed photograph of their daughter, singer Jacqui Dankworth, is framed by the window, and Cleo talks proudly of how Jacqui and her brother Alec used to listen to her practising: "They'd be word perfect by supper."

Cleo is on crutches and was forced to cancel a recent trip to America - "I tripped over a suitcase while I was packing; it was the first time I've ever broken anything in my body" - but she has already rescheduled it for the autumn. Next to her chair are dumb-bells to keep her arms trim, and a biography of the Mitford sisters.

John, also 81, met Cleo when she auditioned for his band. Some years later she left, prompting him to propose marriage: "I think he just wanted a cheap singer. I didn't go back, but I said yes to his proposal." It seems the relationship has matured. "Cleo and I have been married well over 50 years and of course we argue: we always have," he says. "Over time, a relationship becomes like a friendship as well as a love match. These days when we talk, it's often as best friends. In all this time I've never quite worked out how to win an argument with her."

Rather than cutting back on work, John is packing more in than ever. "Before I turned 80, I'd never really thought about age. But I don't feel any less drive to improve, to write new music, to try new experiences. And I'm now a man in a hurry. Sometimes I catch myself resting and I have to force myself to hurry up."

He plays often with people far younger than he is, and enjoys it. "I don't look at people any differently depending on their age any more than I would because of their sex or race. Last night I was rehearsing with a school band. Sometimes I can see they don't know what to call me - should they make allowances for age and call me Mr Dankworth or Sir?"