The Duchess of Cambridge donned a pair of headphones and tried to interpret codes during her visit to Bletchley Park where her grandmother worked.
Valerie Glassborow worked as a civilian member of staff, probably as a duty officer, alongside her twin sister Mary.
Wearing an Alexander McQueen outfit, Kate greeted staff on a visit to mark a year-long restoration project at the Buckinghamshire site.
More top news
The signs were encouraging to commuters going about the transport network the day after a terror attack in Westminster.
Faith leaders from across London say religious communities will "stand together" in the wake of the Westminster terror attack.
Pc Keith Palmer was among the three people killed yesterday in the Westminster terror attack.