The Duchess of Cambridge was sent signals similar to those sent out by the enemy and interpreted at 'spy school' Bletchley Park during the Second World War.
Her grandmother Valerie Glassborow worked at the famous site as a civilian member of staff, probably a duty officer, with her twin sister Mary.
Kate's visit marked a year-long restoration project at the Buckinghamshire site.
More top news
Cloud and rain will continue to spread across Northern Ireland and Scotland through the day. The rain will be accompanied by a strong wind.
Two Birmingham men have been found guilty of funding Brussels airport bombing suspect Mohamed Abrini - known as "the man in the hat".
The actor was best known for his role as Maester Aemon in the TV hit and sitcom Porridge.