Queen Elizabeth II has taken part in a ceremony celebrating the centennial of Government Communications Headquarters (GCHQ), the country's spy agency. During the ceremony, which took place at GCHQ's former building at Watergate House, the monarch unveiled a cryptic plaque with a hidden message that the agency has offered to the public to solve.
After the ceremony, the Royal Family Twitter account posted an encrypted message to the service, with the service promptly replying in a similar code.
Speaking during the ceremony, the Queen — who received intelligence briefings herself for most of the service's existence — recalled how her father King George VI got infuriated with the spy technology of the time.
"I remember my father had one", she said about GCHQ's scrambler telephones, used to keep Royal phone talks secret. "He used to get so cross when it didn't scramble".
"Took some time to heat up and then work. The machines used valves, today replaced by transistors, which needed time to warm up before the equipment would work", she recalled.
GCHQ's director Jeremy Fleming spoke before the Queen and invited guests.
"Our work is not often glamorous or easily portrayed in film", he said. "But over the last 100 years it has saved countless lives, shortened wars, given Britain an edge, and solved or harnessed some of the world's hardest technology challenges".
He added that in order to keep up in this digital era — "to optimise the potential of technologies like artificial intelligence and quantum computing — we know we need to keep reinventing".
The service, which has outgrown its old building, is now stationed in a futuristic-looking ring-shaped building in Cheltenham.