Radio 4 - the cosy middle class enclave of Britain airwaves where poetry vies with the shipping forecast and stimulating debates about the future of farming abounds - has decided to kick off Monday mornings with a new mathematical puzzle feature, inspired by GCHQ.
Why? Because there's nothing more middle class and British than quietly frowning at a meaningless brainteaser over an early morning cup of Earl Grey, pausing occasionally to admire the progress of the Chrysanthemums out of the kitchen window, as your husband pecks you on the cheek and ambles off to work. Is there a problem with Harold? You think momentarily. He seems rather distant of late. Never mind that: pull yourself together. Doesn't do to worry. Here: get back to this puzzle. That's better.
Take the numbers 1, 2, 3, 4, 5, 6, 7, 8 and 9. Insert the fewest numbers of plusses and minuses wherever you want to get to a grand total of 100.
You must keep the numbers in that order, though you can combine numbers as long as they stay in sequence (for example 4, 5 can become 45).
This, for example, is how to do it using six plusses or minuses: 1 + 2 + 34 - 5 + 67 - 8 + 9 = 100.
Easy, right? But can you beat this guy?! He doubts it.
…And if you get bored of trying, remember, there's probably some bread to bake, or a fishmongers to visit, or a marriage to save. Good luck!