Samurai on site!

Staff member "I think he's got a sort of Japanese sword with him?! What should I do?" 
Security "Approach him, ask politely what it is, and explain that we'll need to store it securely while he looks around."

After the gentleman removed his very ornately handled umbrella from it's very posh waterproof carrying case, and opened it to demonstrate it was not a sword, the staff member apologised and retreated in embarrassment. 

We didn't think to check if it was a sword cane, or he was a a Russian with a grudge and a small poison pellet.