We're not too sure he would go unnoticed...
It looks like William wanted to get a bit of spy training in as he has spent the last three weeks learning all about the UK's security and intelligence.
He first visited M16 - where James Bond is supposed to work in the movies - as well as M15 and Government Communications Headquarters in Cheltenham.
M15 concentrates on protecting the UK from terroism and GCH works on potential threats to the country.
In an Instagram post, The Duke of Cambridge said: “Spending time inside our security and intelligence agencies, understanding more about the vital contribution they make to our national security, was a truly humbling experience.
"These agencies are full of people from everyday backgrounds doing the most extraordinary work to keep us safe. They work in secret, often not even able to tell their family and friends about the work they do or the stresses they face."
We can see a movie being made about a prince who turns into a spy now... Watch this space.
