Those of you who’ve never had a real sourdough have ... time-lapse video of the starter as the beasties within give off their CO₂, thus expanding it up inside its container.

Sourdough starter, an alchemy of flour ... On day 1, put flour and water into a 2-litre storage container (a large glass jar works well). Stir together - this is your starter.

Mix together the flour, sourdough starter and 250ml/9fl oz water in a bowl. Add the sugar and salt. Turn out on to a surface and knead for 10 minutes or until the 'windowpane effect' is achieved ...