GCHQ has released a new charity quiz book compiled by government code-breakers, which staff insist is even more difficult than the the so-called ‘world’s hardest puzzle' released by the agency last year.
The book’s authors have said it will take “months” for someone working on their own to work through the puzzles successfully, and must be completed in stages in order to progress through a series of clues.
Over 600,000 people from around the world submitted entries to last year's puzzle, released in time for Christmas by agency director Richard Hannigan.
Three people reportedly came closest to cracking the codes set down by the 2015 challenge, and received a special paperweight and a signed copy of the Alan Turing biography 'Decoded' as prizes for their efforts.
Irish-born David MacBryan, 41, who now lives in Edinburgh, Wim Hulpia, 40, from Belgium, and American Kelley Kirklin, 54, made it to the final round of challenges but were not quite able to finish the task.
One of the puzzle-making team, who wished to remain anonymous, told BBC News: "I don't think there's any coincidence that you find a bunch of people setting these sorts of problems who are also working on the kind of problems GCHQ works on.
"We are faced with problems where there is incomplete information, there is ambiguous information, you have to decide whether you have pushed an angle far enough… that's the sort of thing we expect people to do with these sort of questions."
This year’s book features a forward from Duchess of Cambridge Kate Middleton, whose grandmother served at the code-breaking centre Bletchley Park during the Second World War.
8 of the very hardest maths puzzles
8 of the very hardest maths puzzles
1/8 Crossing the bridge
Four people need to cross a rickety bridge at night. Unfortunately, they have only one torch and the bridge is too dangerous to cross without one. The bridge is only strong enough to support two people at a time. Not all people take the same time to cross the bridge. Times for each person: 1 minute, 2 minutes, 7 minutes, and 10 minutes. What is the shortest time needed for all four of them to cross the bridge?
Claire Backhouse/flickr/Creative Commons
2/8 Number magic
If you multiply me by 2, subtract 1, and read the reverse the result you’ll find me. Which numbers can I be?
Dustin Liebenow/flickr/Creative Commons
3/8 One thousand monkeys
A very big building in which one thousand monkeys are living is lighted by one thousand lamps. Every lamp is connected to a unique on/off switch, which are numbered from 1 to 1000. At some moment, all lamps are switched off. But because it is becoming darker, the monkeys would like to switch on the lights. They will do this in the following way: Monkey 1 presses all switches that are a multiple of 1 Monkey 2 presses all switches that are a multiple of 2 Monkey 3 presses all switches that are a multiple of 3 Monkey 4 presses all switches that are a multiple of 4 Etc., etc. How many lamps are switched on after monkey 1000 pressed his switches? And which lamps are switched on?
Buddhika Weerasinghe/Getty Images
4/8 School lockers
A high school has a strange principal. On the first day, he has his students perform an odd opening day ceremony: There are one thousand lockers and one thousand students in the school. The principal asks the first student to go to every locker and open it. Then he has the second student go to every second locker and close it. The third goes to every third locker and, if it is closed, he opens it, and if it is open, he closes it. The fourth student does this to every fourth locker, and so on. After the process is completed with the thousandth student, how many lockers are open?
Brett Levin/flickr/Creative Commons
5/8 One bulb, three switches
You have three switches in a room. One of them is for a bulb in next room. You cannot see whether the bulb is on or off until you enter the room. What is the minimum number of times you need to go in to the room to determine which switch corresponds to the bulb in next room?
JOEL SAGET/AFP/Getty Images
6/8 Cheryl's birthday
Albert and Bernard just become friends with Cheryl, and they want to know when her birthday is. Cheryl gives them a list of 10 possible dates: May 15, May 16, May 19, June 17, June 18, July 14, July 16, August 14, August 15, and August 17 Cheryl then tells Albert and Bernard separately the month and the day of her birthday respectively. Albert: I don’t know when Cheryl’s birthday is, but I know that Bernard does not know too. Bernard: At first I don’t know when Cheryl’s birthday is, but I know now. Albert: Then I also know when Cheryl's birthday is. So when is Cheryl’s birthday?
Jessica Diamond/flickr/Creative Commons
7/8 Sunday's child
Recently, somebody said: “My grandfather was born on the first Sunday of the year. His seventh birthday was also on a Sunday.” In which year was said grandfather born?
Will Clayton/flickr/Creative Commons
8/8 Probability of having boy
In a country where everyone wants a boy, each family continues having babies until they have a boy. After some time, what is the proportion of boys to girls in the country? (Assuming probability of having a boy or a girl is the same).
WALTRAUD GRUBITZSCH/AFP/Getty Images
Profits from the sale of The GCHQ Puzzle Book will go to Heads Together, a mental health charity campaign set up by the Duke and Duchess of Cambridge and Prince Harry in April this year.
The book also includes a new competition. The first stage involves an intricate sudoku puzzle and a ‘famous faces’ style guessing game - with the remainder of the challenges available to those who purchase the book, on sale from Thursday
Last year’s puzzles generated plenty of discussion across the internet, as challengers swapped clues and ideas on online forums while searching for answers.
The prize for this year’s quiz is yet to be announced, and the closing date for formal entries is February 28.
Now try your luck with three puzzles from the book - answers below
Identify the following:
The answers to these questions come in pairs where each pair differs only in their first letter. Work out the pairs. The pronunciation may not always be the same.
1. One half of a titular TV sitcom couple.
2. British budget clothing and homeware retailer.
3. Type of hat.
4. One of the Channel Islands.
5. River that passes through northern English city.
6. TV space alien.
7. Capital of country with a coastline on the Persian Gulf.
8. Surname of an England football captain.
9. An Irish county.
10. An English city that is a county town.
11. One of the official languages of the fourth largest country in Europe.
12. District of South East London.
My first is in Finland but not in Finnish
My second is in Estonia but not in Estonian
My third is in Albania but not in Albanian
My fourth is in Sweden but not in Swedish
My fifth is in Germany but not in German
My sixth is in Iceland but not in Icelandic
My last is in Wales but not in Welsh
My whole is in England but not in English
Where am I?
They are the first letters of Monopoly squares:
Go, Old Kent Road, Community Chest, Whitechapel Road, Income Tax, King’s Cross station, The Angel Islington, Chance, Euston Road, Pentonville Road, In Jail/Just Visiting, Pall Mall, Electric Company, Whitehall, Northumberland Avenue, Marylebone station, Bow Street, Community Chest, Marlborough Street, Vine Street, Free Parking, Strand, Chance, Fleet Street, Trafalgar Square, Fenchurch Street station, Leicester Square, Coventry Street, Water Works, Piccadilly, Go To Jail, Regent Street, Oxford Street, Community Chest, Bond Street, Liverpool Street station, Chance, Park Lane, Super Tax, Mayfair.
The pairs are:
1. Terry 9. Kerry
2. Matalan 11. Catalan
3. Panama 7. Manama
4. Jersey 5. Mersey
6. Mork 10. York
8. Beckham 12. Peckham
We hope you weren’t put off by any of: (John) Terry/Kerry, (County) Cork/York, Nottingham/Mottingham or Lune/June!
Londres. Each line refers to a letter which appears in a country’s name in English, but not in the native language.
My first is in Finland but not in Suomi: L
My second is in Estonia but not in Eesti: O
My third is in Albania but not in Shqipëria: N
My fourth is in Sweden but not in Sverige: D
My fifth is in Germany but not in Deutschland: R
My sixth is in Iceland but not in Island: E
My last is in Wales but not in Cymru: S
My whole is in England but not in English: LONDRESReuse content