Bomb disposal experts have carried out a controlled explosion on a mortar found in a park in Lancashire. The device was discovered by metal detectors at the Old Tram Bridge in Avenham Park, Preston, on Saturday at about 16:00 BST. The area was cordoned off by the police and customers in a nearby cafe were evacuated. Police said the mortar - believed to be from World War Two - was detonated by experts from the Army.