Bomb disposal experts carried out a controlled explosion on Wimbledon Common when a brother and sister unearthed an unexploded WWII hand grenade without its locking pin.
Tony Burcombe, 30, and Lara Sparrow, 37, were scouring an area near to the windmill with their metal detectors when they made the explosive find at 5pm on Tuesday, March 27.
Mr Burcombe said: “We had been there all day and we were nearly at the windmill in the woods. It was getting toward early evening and my sister shouted over to me.
"She had unearthed a live WWII hand grenade. By the time she realised what it was she already had it in her hand.
"It was buried very shallow, less than an inch.
“I took it from her and put it on the ground very carefully as there was no pin in it.”
The pair immediately called the police, who condoned off half-a-mile square, and the bomb disposal team carried out a controlled explosion of the pineapple hand grenade.
The area used to be an Army training ground during WWII.
Norman Plastow, president of the Wimbledon Society and author of Safe as Houses: Wimbledon At War 1939-45, said: “There were certainly ammunition dumps near the Queensmere and over the years several bombs have been unearthed after the Germans dropped them during the war.
"This is the first case I have heard of hand grenades being discovered but we know there are several bombs still down there.”
While this has been their most shocking find, Mr Burcombe, who has been metal detecting for about a year, recently uncovered a silver 1556 Elizabeth I sixpence.
Mr Burcombe and his sister said they were unaware of the Commons Act of 1871, which prevented them from metal detecting on common land.
Police said: “We were shocked and in fear of what could possibly happen, and the safety aspect of trying to deal with it.
“In situations like that you have to deal with the matter.
“You wouldn’t want to leave it there in case children or anyone got hold of it.”