World War Two mine to be blown up off Portland A mine laid by British forces off the Dorset coast during World War Two is set to be detonated later. The device was discovered close to the breakwater off Portland on Wednesday and a warning issued to shipping. A Royal Navy bomb disposal team has moved it further out to sea to be destroyed. It is believed to have been laid as part of defence measures to prevent German vessels entering British waters during World War Two. Lt Peter Davis of the Royal Navy said the bomb had been a "random find" by divers during a seabed survey. Given the age of the ordnance, the explosive charge within the mine is likely to have degraded over time. It should only be a small column of water that's generated in the area," he added. The controlled explosion, scheduled for early afternoon, is not likely to be visible from the shore.