Here's another lateral thinking puzzle to tease your brains over Christmas. There's a simple explanation to this one and yet the solution remains tantalizingly elusive.

Two fathers take their sons fishing and each of them catches a fish. However, when they get home there are only three fish.

How can this be when none of the fish were lost or eaten on the way back?

If you think you know the answer why not e-mail it to puzzle@controlinmotion.com? There are prizes for the first ten correct answers we receive in January.