UPDATE: Police order Gunwharf Quays evacuation by 11pm over unexploded German 500kg Second World War bomb

Police have been telling businesses that the centre will be closed off from about 11pm.

At about midnight, Royal Navy bomb disposal experts will tow the bomb into open waters 1.5 miles east of the Isle of Wight to perform a controlled explosion - the explosion is likely to take place in the early daylight hours of tomorrow.

Promoter Eskimo 11 posted on Facebook that its event at Tiger Tiger was cancelled.

‘Important – We have just been told all of Gunwharf Quays will be closing shortly due to an incident in the harbour,’ the promoter said in a Facebook post.

‘This means Tiger Thursday will have to close. We will keep you updated as events unfold.’

One worker at a venue in Gunwharf Quays, who asked not be named, said: ‘There’s police on the site.

‘I know everyone has to be evacuated by 11pm.

‘There’s police in Gunwharf Quays and around Portsmouth.

‘They won’t tell me (details).

‘We’ve got to get them out by 11pm.’

George David, 27, and pal Emily Jane, 20, both from London, were in Grosvenor Casino having a meal.

George said: ‘We were in the casino and they stopped the bar and food.

‘We were having a meal and there was an announcement saying everyone had to leave by 11pm.

‘Ten minutes later on they said we’re closing at 20 past nine, we want everyone out as soon as possible.’

He said it was unusual no-one had given a reason for the imminent closure.

He added: ‘For something so important, let’s face it if they have got to close Gunwharf there’s (potentially) millions of compensation, so they have to be closing it for a good reason.’

The device was found by a barge carrying out dredging works ahead of the arrival of the Navy’s new 65,000-tonne aircraft carrier – HMS Queen Elizabeth – next spring.

It’s not thought that the removal or the detonation will affect traffic in the harbour.