IT was the dramatic bomb scare which caused a Hampshire shopping centre to be evacuated.

But the controlled explosion of a Second World War bomb went off with such a small blast that disposal experts thought it had failed to explode.

The 1,102lb (500kg) German device was destroyed this morning by specialist bomb disposal teams.

It had been dislodged from the seabed in Portsmouth Harbour on Thursday night, causing restaurants, bars and a nightclub on the waterfront Gunwharf Quays to be evacuated It was discovered during dredging work to deepen the harbour entrance for the arrival next spring of the Royal Navy's new aircraft carrier, HMS Queen Elizabeth.

Navy disposal experts towed the device into open waters, about 1.5 miles (2.4km) east of the Isle of Wight, where the controlled explosion could be safely carried out.

The device was detonated at 7am - but because there was no plume from the explosion, the bomb disposal team believed it had not worked and planned to make a second attempt.

However, when Navy divers went down to the seabed to inspect it, they found it had exploded as planned.

Commander Del McKnight, commanding officer of the RN Fleet Diving Squadron, said: ''We believe there had been some corrosion on the mine, the explosives inside the mine were corrupted so there wasn't a high ordnance.

''It's always a bit disappointing when it's not as large and explosion as expected but actually the device has been rendered safe, it has been split open and the explosives have been gathered up by my diving team.''

Describing the operation, he added: ''It is dangerous - the fuse can always reactivate and set the mine off or the bomb off, but it had been there for some time so it should be relatively safe.

''It is dangerous stuff but the boys know the risk and minimise those as much as possible. We minimise the number of people making approaches to a device so if there is a casualty it is minimised.''

A Second World War torpedo was also found earlier this month by the dredging operation and it too was exploded at sea.

Cmdr McKnight said it was likely more ordnance would be found while the dredging work continued.

He said: ''It is something we are aware of, we are expecting it to happen. We had a torpedo that was found here not a couple of weeks ago so we are aware of it and we are on call at 10 minutes' notice to move at all times to deal with incidents all round the UK.''