Remember how one of the UK's intelligence agencies set a fiendishly difficult quiz right before Christmas? Well, now it's published the answers, so you can stop scratching your head. GCHQ, the agency which set the puzzle, claims to be "delighted with the interest shown" in the puzzle but notes that "no-one found the four additional intended answers involving further reinterpretation of x as a multiplication sign" in one part of the final section of the puzzle. Which means that, technically, nobody actually solved the entire thing.
That's despite many team efforts from across the internet. GCHQ notes that "many people worked in virtual teams over various web forums to tackle many of the questions together, with some syndicates developing small computer programs to test possible mathematical combinations and reach a solution more quickly". And still no fully correct solutions!
So, what were the answers then? Well, you can read all 23 pages of them right here. But the general chain of solutions saw the first (straightforward) part of the puzzle create a QR code which then took players to the next stages: a web link maze of tough questions involving sequences, codes and odd-one-outs.
The solution to the grid sharing puzzle
That was followed by some word puzzles, then number puzzles and finally a series of "miscellaneous puzzles" — including, but not limited to, crosswords, word searches, chess schemes and pattern-matching puzzles. Oh, and a registration problem that created a picture of a duck. Obviously.
GCHQ claims that a maths puzzle in the final section was what caused the most headaches for valiant solvers. But maybe with the solutions in front of you, it will make a little more sense. Maybe.