Spy agency GCHQ has sent a cryptic tweet to the Queen after she attended an event to mark 100 years of the intelligence agency, but are you able to crack it?
The coded message which read "SVOOL BLFI NZQVHGB GSZMP BLF ULI XLNRMT, RG DZH Z TIVZG WZB" was sent from GCHQ's account to the Royal Family's after the Queen unveiled a plaque at Watergate House, the agency's original headquarters.
Scroll down for the answer to the mind-boggling phrase
The message was a nod to the code-breaking minds of Bletchley Park that helped establish the intelligence institute 100 years ago.
During the Second World War the agency moved staff to Bletchley Park where Alan Turing was instrumental in breaking Enigma-encrypted communications, making a significant contribution to the Allied victory.
Queen marks GCHQ centenary and recalls king getting ‘cross’ with scrambler phone
During her visit the Queen also met Ruth Bourne, 92, a former Bletchley Park code breaker.
When the subject of scrambler phones – used to keep important conversations confidential – was mentioned, the Queen said: “I remember my father had one, he used to get so cross when it didn’t scramble.
"Took some time to heat up and then work."
So, how to crack the code...
The code was originally posted to Twitter at 14.16 on Wednesday, leaving many social media users dumbfounded for almost three hours, before the message was revealed just after 5pm.
GCHQ revealed the code was encrypted using the Atbash cipher and confirmed what some social media users had already guessed - the original message was: "Hello Your Majesty. Thank you for coming, it was a great day."
For those who don't know, Atbash is a very common, simple cipher that was originally intended for use in Hebrew but can be adapted for English.
To decipher an Atbash code, the alphabet must be reversed, meaning 'A' becomes 'Z', 'B' becomes 'Y' and so on.
An easy way to crack a coded Atbash message is to write the alphabet in its correct order and then backwards underneath, then use that to work out each letter's corresponding letter.