The suitcases are packed. The neighbour has agreed to feed the cat. And detailed instructions have been left for the care of the more cultured pet. This one can be tricky. Its food must be weighed out precisely. It enjoys

daily fresh air. It becomes unruly if neglected, occasionally smashing its own cage.

“House-sit a WHAT?” says the woman who answers the phone at Animal Aunts.

“A sourdough starter.”

Gillie McNicol, who founded the company in 1987, comes on the line and says smoothly: “Animal Aunts will look after any being whether it be a sourdough or a hedgehog. My husband has a sourdough that requires daily attention. His alarm just went off in the office, saying: ‘Sourdough! Sourdough!’”

Sourdough-sitting may sound bizarre, but it is the logical consequence of several food trends over the past eight years. The real bread movement has gained momentum. The Great British Bake Off has inspired a new generation of homebakers. And sourdough has emerged as the UK’s most fashionable dough (see the success of the sourdough pizza chain Franco Manca, the proliferation of £2-a-slice-of-toast joints in Hackney, the momentum of the Herman cake).

Once you start finding people who have sat sourdough or procured a sitter, it’s hard to stop. One leads to another. Roger Murray, a mount-maker at the Victoria & Albert museum, “sat a friend’s starter. He brought round two jars of this white liquid, gave me a printed instruction sheet and a couple of bags of flour. They need feeding every day. There was this horrible moment when I handed it over. I didn’t know what it was supposed to look like.” The stakes were high. The sourdough had a name – Horace – which indicates his friend’s degree of attachment. An anxious wait followed, until a text arrived saying: “I’ve baked with it and everything’s fine.” As a thank you, Murray now bakes with Horace’s offspring.

This summer, Kelda Wallis, 45, a social media manager from south London, asked a neighbour to feed her starter, along with the cats, when she went on holiday (though when she got back she checked on the cats first). Dani Redd, a student, has used a sitter. “I used to email my friend while I was away and say: ‘Have you fed my sourdough baby?’” There has even been a “sourdough hotel”.

There are other options. You can refrigerate your starter, or spread it thinly on a baking mat, dry it, and store the flakes in an airtight container. Finding someone to sit your sourdough is taking things too far, isn’t it?

“It is a bit odd, but I knew exactly what you meant,” says Andy Lawson, a tutor at Bettys cookery school. He has experience of starter-sitting for friends. “It had travelled over from Poland. My life was a bit busy. I didn’t have the respect for it. I left it out of the fridge and it turned into a brown sloppy mess. It basically ate itself. I didn’t give it back.” Now he has a culture of his own, named Frank, and life is different. (Raising sourdough is like parenting: you have to be ready.) Lawson is fresh from a holiday in Wales. “I took the starter with me. I thought it could just jump in the back of the car.” If he goes further afield, he will find a sitter. “But I’d like them to be a bit more clued up than I was.”