Could You Crack GCHQ's Latest Brainteaser?

The intelligence and security organisation that is responsible for protecting the UK from terrorism and cyber attacks has released a tantalising coded tweet for the public to unravel - in the form of emojis.

It is part of a new set of brainteasers by the country's top codebreakers to mark the intelligence agency's centenary year in 2019.

The GCHQ Puzzle Book 2 will be released on October 18, with all proceeds from sales going to the Heads Together mental health campaign spearheaded by the Duke and Duchess of Cambridge and Duke of Sussex.

A GCHQ spokesman said: "We were delighted with the success of our first puzzle book, which raised over £330,000 for the Heads Together campaign, an important cause to change the conversation around mental health.

"To mark our centenary next year in 2019, we have created a new puzzle book celebrating our 100-year history of keeping the country safe."

During the Second World War, code breakers at Bletchley Park helped break Germany's Enigma code.

Its existence was publicly revealed by the journalists Duncan Campbell and Mark Hosenball in a celebrated case in the 1970s.

Now, the code breakers will release a series of codes for the public to break - and following criticism from the first book, the aim is to make the second slightly easier, but it will still feature some tougher puzzles to crack.

The second book will also feature an authentic entrance exams set for would-be recruits.

It will also include anecdotes about the people, technology and partnerships that are central to GCHQ's mission.