school, she started playing the piano for a keep-fit class during the second world war – “just for something to do during the blackouts, really” – and eventually took over in her 40s when the previous instructor retired. At its peak, Allen’s class had more than 18 regulars, each paying £1 a time. But, these days, her flock is diminishing fast – during the teabreak, the ladies discuss a funeral that most of them had attended that week for one of the younger members of the group who had just died, aged 68, from motor neurone disease. Allen is the oldest, followed by her sister. The baby of the group is 60-year-old Jean Cunion, who credits the group with supporting her through a difficult time when her mother died. She is somewhat embarrassed to admit that she is perhaps the least fit of the group. “I remember, the first time I came, Margaret said: 'Who’s that huffing and panting?' and I had to admit it was me.” Ruth Steere, 76, marvels at how Allen never misses a trick, despite always having her back to the class: “She always shouts at us if we go wrong. She’s remarkably good at knowing what we are doing.” Allen, a keen dancer, has never done any formal training to be a fitness instructor. Instead, she choreographs her own moves based on five tapes from the BBC’s first ever fitness guru, Eileen Fowler, who died in 2000 when she was 93, Allen’s age