First, the base must consist of boring brown bread; custom dictates that only the highly processed supermarket kind will do. The most typical filling is sliced cheese, especially a brown, sweaty type made from cream and goat’s milk, known as ‘brunost’. It has an unusually low melting point, so it perspires at room temperature – and it’s also highly flammable (the cheese made global headlines back in 2013 when a lorryload caught fire and burned for five days). Other options include cheese from a tube or liver pâté.

“The pâté is not like you’d find in other Nordic countries,” says Sagatun. “It’s more bland in a way, and it’s not that fresh. You can stock it for years and years.”

Sagatun is keen to point out a few classic blunders, such as piling on the fillings or using more than three or four slices of bread. “It should be just what you need when you are hungry, but not more than that,” he says. It’s also taboo to add salad or slices of delectable cured meat. To avoid stern looks from colleagues, those aiming for a fancier version can try mackerel in tomato sauce or cod roe caviar instead – as long as it’s from a tin or a tube. Sagatun says “this is as exotic as it gets”.

Another hallmark of the matpakke is the addition of small, bread-sized squares of mellomleggspapir – between-layer paper – between each slice of bread; these can be peeled off as you eat your way through the layers. The lunch is usually eaten with a thermos of hot tea or coffee.

But regardless of what you put in your matpakke, there are other things that we can learn from Norwegian lunch culture. According to Holm, it’s unusual to skip lunch, and people tend to have it at roughly the same time of day, every day.

As it happens, this is the first cardinal rule of improving your work output, regularly advocated by productivity gurus and splashed liberally across the pages of self-help books: have a daily routine.