209 oddly-shaped pieces, one shape, and a £1 million prize
In June 1999, a puzzle called Eternity went on sale: 209 identical-area but irregularly shaped pieces had to be fitted together, edge to edge with no gaps or overlaps, into one large near-regular dodecagon. Its creator believed it could take years, maybe decades, to crack, and offered a four-year window to claim a £1 million prize. How long did it actually survive?
Reveal the answer
Less than a year. Cambridge mathematicians Alex Selby and Oliver Riordan wrote a custom search algorithm and found a valid solution by May 2000, collecting the £1 million that October — nowhere near creator Christopher Monckton's own six-clue 'intended' solution, which has never been matched. A second, different solution was later found by Guenter Stertenbrink.
— Christopher Monckton (creator), Eternity puzzle — Ertl Company, 1999