William and Kate
Kate Middleton arrives at the World Mental Health Day celebration with Heads Together at the London Eye, London Chris Jackson/ Getty Images

Kate Middleton's grandmother Valerie Glassborow was one of the Bletchley Girls, who had served during the Second World War and was responsible for intercepting enemy codes for decryption. While reports suggest that Glassborow's wartime work at the Bletchley Park code-breaking station was more of a family secret until now; Princess Kate has recognised her grandmother's work in a new book.

The Duchess of Cambridge recently addressed her grandmother's contributions during the war and paid tributes to her in the form of a foreword in the first-ever puzzle book released by GCHQ or the UK's Signals Intelligence and Cyber Security agency.

"I have always been immensely proud of my grandmother, Valerie Glassborow, who worked at Bletchley Park during the Second World War," she wrote admiring the great efforts put up by her late grandmother and her colleagues.

"She and her twin sister, Mary, served with thousands of other young women as part of the great Allied effort to break enemy codes. They hardly ever talked about their wartime service, but we now know just how important the men and women of Bletchley Park were, as they tackled some of the hardest problems facing the country."

Aimed at inspiring and challenging readers, the puzzle book was released as a part of the Heads Together campaign, which is a joint effort by Princess Kate, Prince William, and Prince Harry to raise awareness on mental health. In fact, all proceeds from the books will be going to this social mission.

In the touching foreword, the mother-of-two also went on to discuss about her ongoing campaign and the need for an open discussion when it came to mental health problems.

"William, Harry and I are very grateful that this book is supporting our Heads Together Campaign. I hope it will not only amuse and challenge readers, but help to promote an open discussion of mental health problems, which can affect anyone, regardless of age or background," she wrote.

"Together, we are aiming to change the national conversation around mental health from stigma and fear to openness and understanding."

Facts about the Bletchley Park code-breaking station

Celebrated scientist Alan Turing, whose life during the Second World War has been made into a movie – The Imitation Game starring Benedict Cumberbatch and Keira Knightley – also served for top-level decryption at the Bletchley Park.

BBC reports that the women working as coders at Bletchley would be typically referred to as "girls" and were relegated to low-level clerical work.