GCHQ reveals toughest Christmas challenge to date - can you complete it?

GCHQ has revealed its annual Christmas challenge - and says this year's is the toughest to date.

The challenge is presented in the form of a Christmas card sent by Director Anne Keast-Butler.

The card features a rare image of a snow-covered Bletchley Park mansion, the agency's war-time home.

It was taken in January 1940 before a photography ban was introduced and was more recently discovered in the personal family album of codebreaker Joan Wingfield.

While the Christmas challenge has been designed with schools and colleges in mind, anyone can take part and GCHQ is encouraging the public to test their wits against its puzzlers.

It features seven complex puzzles which were created by GCHQ's mastermind puzzlers. They test a range of skills including problem-solving and teamwork.

For three years, the annual GCHQ Christmas Challenge has aimed to inspire young people to study STEM subjects, as well as provide insight into the agency’s work.  

The agency has included a bonus puzzle this year, to encourage adults to get their thinking caps on.

The GCHQ Christmas Challenge is designed to test lateral thinking, ingenuity and perseverance skills, all needed by those who work at GCHQ to help them keep the country safe. 

More than 1,000 schools have signed up for the challenge so far.

It can be downloaded on the GCHQ website.