A massive plume of smoke billowed over the Thames Estuary today as a bomb disposal squad destroyed a Second World War German mine.
Royal Navy experts said the hefty weapon had the potential to go off "at any moment" before it was caught in the nets of a small fishing boat earlier this week and placed on the sea bed.
The mine, packed with 750kg of high explosives, was brought to the surface by divers before it was towed to a safe spot and detonated - propelling a cloud of ash and water more than 120 metres into the air.
It took the four-man Royal Navy team, part of Southern Diving Unit 2 (SDU2), several hours to transport the weapon in a rigid inflatable boat to the selected location, two miles from Warden Point, Isle of Sheppey, in Kent.
This came after the device - measuring one metre in diameter and two metres in length - was carefully raised from the sea with a specially designed mine-lifting air-bag.
The "delicate" operation involved establishing a one-mile safety zone around the weapon before it was set off.
Lieutenant Dan Herridge, Officer Commanding SDU2, said it had posed a serious danger and could not be destroyed where it was first found - close to an underwater electrical cable.
"Due to the amount of high explosive in the mine, which posed a significant risk to public safety, it was necessary for the mine to be lifted and taken to a safe location to be dealt with," he added.
Mines such as this one, which were usually dropped by parachute, were designed to sink big ships, sometimes snapping them in half.
"Because of the construction of them, they are all fully intact and ready to go," Lieutenant Herridge added.
"This was quite a large one. Potentially it could have gone off at any moment."
The resulting explosion "punched up quite high" because it took place in only 10 metres of water, he said.
The "high order" detonation followed a failed attempt to destroy the mine yesterday.
Last week divers from the same unit removed the remnants of a German war-time V2 rocket which was found submerged in mudflats.
The 4ft-long section of the Second World War missile was pulled out at low tide from the River Stour between Harwich, Essex, and Felixstowe, Suffolk.