Navy bomb disposal experts were scrambled to the Isles of Scilly after an unexploded device was found on a beach on Wednesday afternoon.
A member of the public came across the explosive hidden amongst seaweed during a dog walk at Porthellick on St Mary’s.
Local police cordoned off the beach and warned people to stay away from the area.
Police Constable Faye Webb was first at the scene.
She said: "I wasn't particularly worried. I could see it was some type of flare but obviously these things can be dangerous and explosive.
"We have got protocol to follow. I certainly wasn't prepared to touch it."
PC Webb made a call to the Ministry of Defence, who mobolised a team of four Navy bomb disposal experts from Plymouth.
They arrived at the beach in an RNAS Culdrose helicopter at around 3pm.
It was discovered the foot and a half long device was a phosphorous flare from an aircraft, which could be dangerous if set off accidently.
The bomb disposal team dug a trench and used a controlled explosion to destroy the device.
"It was a fairly big explosion. It did make a bit of a boom. I was particularly impressed. It wasn't a usual day on Scilly," added PC Webb.