As for the future – and after Twinnie and Sigsbee teach the latest addition to the family to swim and catch fish – John says he hopes to hear the patter of tiny penguin feet again next year.
He is trying to find out if a hatching a chick aged 24 will be some kind of record.
Andrew Owen is head of birds at Chester Zoo, which is part of an international conservation programme.
“It’s fair to say that 23 is a good age for a penguin in general, let alone in terms of successfully hatching an egg,” he says.
“We had a 21-year-old female successfully hatch this year, but it is unusual.”
Longevity runs in Twinnie’s family. Sewerby Hall was home to her mother, Rosie, one of the oldest known Humboldt penguins.
Rosie, who has lived at the park since 1990, died in 2023 at the age of 32.
And Twinnie still has a long way to go to match what is believed to be the oldest Humboldt. Spneb, from Cornwall, recently celebrated her 37th birthday with a cake made of ice and her favourite fish – sprats.