The word AMBULANCE is printed on the front of an ambulance back-to-front, so that a driver ahead who glances in the rear-view mirror reads it the right way round. On the van itself, which letter is printed nearest to the left-hand end of the word?

A mirror swaps left and right, so the printing on the van must be the word in reverse order: E, C, N, A, L, U, B, M, A. The letter at the left-hand end is therefore E, the last letter of the ordinary spelling. The trap is A — the letter that begins the word when it is read normally, and the one most people name without thinking about which end the mirror moves it to.