Queen Elizabeth II has unveiled a monument to hundreds of mathematicians and cryptographers who worked in secret during World War II to crack Nazi Germany's communications codes.
The monarch and her husband visited Bletchley Park northwest of London, former home of the top-secret Code and Cypher School, whose staff cracked Adolf Hitler's supposedly unbreakable codes.
Historians believe their work shortened the war by as much as two years, but they were forbidden from disclosing their work for decades afterward.
The queen praised the men and women who worked "in the greatest secrecy, so much so that some of their families will never know the full extent of their contribution."
She unveiled a stone obelisk inscribed with the words "We also served."