When Ulrich Weigert turned 100, there were five birthday parties and cards from the Queen and a government minister.

But on the downside, he managed only a 1.6 kilometre country walk, rather than the two kilometres he normally covers. At least he did not miss his regular art class on his birthday morning, or his yoga group later in the week. And dipping into a stack of broadsheet newspapers and journals helps to keep his mind active.

The German-born analytical chemist likes to keep busy. Hailing from an illustrious line of Jewish scientists and doctors, he worked in Sheffield's steel industry after escaping Nazi Germany. Until the age of 94, he gave lectures to a lobby group campaigning for cleaner drinking water.

Leaping out of his chair at the Sheffield care home where he now lives, Mr Weigert points proudly to the framed picture of a fox he took aged 97 while indulging in a spot of wildlife photography. Other photos on the wall were shot while cross-country skiing in his native Bavarian Alps at the age of 80.

"I didn't bother with skiing insurance," he explained chuckling. "My grandfather was 89 when he died, my father 97. My wife, Barbara, is 88. Statistics show that most of the people who reach 100 are women, so I'm trying to redress the balance." Mrs Weigert, another German refugee, maintains their nearby family home and visits him regularly. They have been married for 60 years.

Mr Weigert fled Germany for Manchester, aged 18, in 1932, just weeks after finding out he was Jewish. His father - a famous Bavarian doctor who once treated the daughter of former British Prime Minister Stanley Baldwin - had brought up his children as Christians to protect them from antisemitism.

"At school, aged 17, we learned that Jesus Christ was the most wonderful person and there were horrible people who persecuted him. They were called Jews," Mr Weigert recalled. "When I told my father what I had learned, he got very worried and explained to his children that we were Jewish and threatened by the Nazis' ideas."

Arriving in Britain, he was sent to his second cousin in Manchester, exiled German-Jewish physicist Sir Rudolf Ernst Peierls, who had a major role in Britain's nuclear programme and who was later pivotal in fighting nuclear proliferation.

Mr Weigert studied chemistry at Manchester University and went on to be involved in the discovery of how steel manufacturing was poisoning the British countryside and killing cattle. But during the war, he was interned as an enemy alien.

"When I was first arrested in 1939 the enemy alien tribunal asked me if I had any good references. I got off by telling them my father had treated Baldwin's daughter, Lady Huntington-Whiteley," he explained.

"But in 1940, all the previous classifications were thrown overboard when Churchill said 'collar the lot'. I was behind barbed wire on the Isle of Man and was then sent to Canada. If you ask me what are the three worst human inventions, they are barbed wire, the cigarette and the atomic bomb."

He was also no fan of revenge. "The position is tragic within Israel today but also in Jewish communities. I see there are these tensions over what happens in Gaza, and boycotts.

"I'm upset by the recent past in Gaza. It only creates more bitterness for the future. In a way you can understand what happens but revenge is never a good thing. And here my father gave me a very good example.

"Despite all that happened, losing his mother and his brother to the Nazis, my father was never for revenge. After the war, when the people in our old town found out he was still alive, they wanted him back as their chief doctor in Sonthofen. He worked in the hospital until he was 75 and was honoured with the freedom of the city, aged 90."

Mr Weigert's daughter, Suzie, said he was an inspiration. "He never lingers on the past but wants to be part of today.

"Very few people his age are so animated about today. To forgive people and concentrate on their strengths and enjoy life with 100 per cent of your being while chuckling at it - that is my father."