![[ image: width=150]](/olmedia/55000/images/_56770_bomb_tail.jpg)
![image: [ Bomb disposal experts say poor conditions have left them with only one alternative - to detonate the 750kg bomb ]](/olmedia/55000/images/_56770_muddy300.jpg)
The public were warned that the blast, which will be carried out under controlled conditions, could cause some damage to surrounding houses in the town.
The decision to detonate the 750kg bomb was taken after police and Army experts decided that continued efforts to defuse it would take too long.
Poor conditions made the operation almost impossible. The bomb, discovered on a building site, has remained buried in water-logged clay.
Superintendent Ian Maidment from Wiltshire Police announced there was no other option than a controlled explosion.
"The decision was made following specialist advice from bomb displosal experts who say it is impossible to immobilise the bomb in its current situation," he said.
Around 1,100 people are now facing a second night in emergency shelters or at the homes of relatives.
The unexploded bomb was one of two wartime devices discovered on the building site on Friday.
After part of the town was cordoned off, Army experts were called in to deal with the explosive devices.
A single expert started working under floodlights on Friday night to diffuse the 750kg bomb.
Army spokesman Captain Edmund McMahon-Turner described the bomb as a very dangerous piece of equipment which could explode at any moment.
The residents who were evacuated will not be able to go back home until the bombs are made safe.
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