When is a one-in-25 billion shot not a one-in-25 billion shot? Let us eggsplain.

Alan Millar got a particularly bountiful treat when he ordered ham, egg and chips (aka fries) in a British pub: staff who cracked the two eggs to fry for the meal found one with a double yolk and one with a triple yolk.

Unfortunately his meal at the Gloucester Old Spot pub has led to some dodgy statistical reporting with several newspapers claiming such a combination has only a one-in-25 billion chance of happening.

That would be true if multiple-yolk eggs appeared entirely randomly rather than in clusters. In practice such eggs are often intentionally packaged together by staff on production lines with the intention of “liberating” the carton to take home for an extra-yolky treat, an intention that doesn’t always pan out.

Economist Tim Harford explains more about this probability flaw — and its parallels with the 2008 financial crisis — in his book The Undercover Economist.