GCHQ Christmas puzzle likely to be worked out before festive season

Spoiler alert: series of brainteasers and codes put online by spy agency to 'exercise grey matter over holiday period' has nearly been solved after one day

Perhaps being one of the country's leading cryptologists isn't so difficult after all.

When a mysterious puzzle was posted on the website of the government spy agency GCHQ on Wednesday, its creators presumably hoped it would continue to fox recipients well into the festive season.