We have another old but good logic puzzle this week. It's amazing how many of these "standard puzzles" people have not heard.
A King died and the elder of his two sons prepared to ascend to the throne. The family assembled to hear the reading of the old King's will, and found a little surprise in it.
The King had specified that he would be succeeded by the son who had the slowest horse. And as it happened both Princes owned just the one horse.
[Yes, we know that this isn't how a hereditary monarchy works, but this was a long time ago - don't spoil the puzzle!]
A race was duly held and the Prince who would become King selected. The question is, how did they organise the race?
The obvious problem in determining the slowest horse is how to prevent the horses being held back to look slower than they are. Of course, if you are trying to find the fastest horse, both riders would try their utmost.
And there is the answer - each Prince rides his brother's horse.