In a new series about the dishes that mean the most to us, Andi Oliver meets cookery writer, presenter and GBBO star Briony May Williams to sample her home-made soda bread. Briony makes soda bread just as her incredible Granky did, using a recipe that's now over 100 years old.

Andi and Briony wonder how on earth anyone discovered that using ash from a fire makes a delicious risen loaf, get stuck into the science of acidulation and saccharomyces cerevisiae, and Andi has a bread-related brainwave which will transform the way you roast a chicken and will quite possibly change your life.

Food Scientist: Kimberley Wilson
Food Historian: Neil Buttery
Producers: Victoria Lloyd and Lyndsay Fenner
Series Producer: Lucy Dearlove
Executive Producer: Hannah Marshall
A Storyglass production for BBC Radio 4