Kate, 32, looked beautiful in navy as she visited the famous estate in Buckinghamshire, where codebreakers worked during World War II to crack messages being sent by the enemy.
For the duchess, the engagement had a personal connection as well, as her late grandmother Valerie Glassborow (later Middleton) had worked at Bletchley during the war as a duty officer.
It's believed that Valerie worked at what is now named Hut 6 at Bletchley, which is among the recently restored huts. Kate will be given a tour of Hut 6 and other areas of the park during her visit, as well as speaking with a woman who worked alongside her grandmother.
According to Bletchley Park records, her paternal grandmother Valerie worked alongside twin sister Mary as Foreign Office Civilians in the Cover Management Y section, which managed the interception of enemy messages for decryption.
It's thought the twins were among the first to know the war had ended.
The duchess will also speak with other World War II code breaking veterans, view interactive exhibitions and demonstrations, and meet the team who oversaw the restoration. She will also be invited to plant a tree.
Kate's visit was to mark the completion of Bletchley Park's restoration to its World War II glory, allowing visitors to see how the estate ran as a Government Code and Cypher School during the war, and what life was like for codebreakers.
The transformation cost £8 million and was a Heritage Lottery Funded project.
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