A scientist and inventor who founded a scientific instruments firm in Belsize Park – and once slept in a volcano – has celebrated his 100th birthday.

Ham & High: James Nelson with friend Sara Mark. Picture: Nigel SuttonJames Nelson with friend Sara Mark. Picture: Nigel Sutton (Image: © Nigel Sutton email pictures@nigelsuttonphotography.com)

James Nelson reached his century on Friday before marking the milestone with a party at the Henderson Court Resource Centre in Fitzjohn’s Avenue, Hampstead, yesterday.

The Scottish chemical physicist enjoyed a slice of cake surrounded by old friends and fellow users of the Age UK-run centre.

He said: “I feel the same as I did. It doesn’t mean much to me, I have no worries. My secret is pure thoughts.”

Mr Nelson founded McCrone Scientific Limited in 1964 from his home in Lyndhurst Road, where he still lives, before moving the company to Belsize Lane.

He developed instruments that are still used today, including the McCrone Micronizing Mill, and his areas of expertise included asbestos and gemmology.

His friend Sara Mark, 72, of East Heath Road, Hampstead, who worked at McCrone for 40 years, revealed he has led an active and intrepid life – even spending a night in a Lanzarote volcano with his late wife Doris.

“He’s such a charming man,” she said. “He’s always had a great sense of humour. It was lots of fun working together.”

Laurie White, manager of the centre, said: “He’s been a member for 10 years and he still comes for exercise classes, which obviously must be working.”