Armed with sub-machine guns, they are a stark reminder of the threat we now all face.

Anti-terror officers have been deployed at shopping centres in Norwich and King's Lynn. Last night, there was an armed presence outside Lynn Corn Exchange, as it hosted the monthly Comedy Club.

Norfolk police said we can expect to see an increased police presence, including armed units, at key locations around the county.

Security officials raised the threat level to critical - meaning meaning an attack not only remains highly likely but a further attack may be imminent.

Chief constable Simon Bailey said: 'There is no specific intelligence relating to Norfolk however the public would expect us to respond accordingly to this raised threat level.

'As a result members of the public will see an increased policing presence at key locations – primarily those with high-footfall and we are reviewing key events over the coming weeks.

'I would ask the public to remain calm but alert – if you see anything which causes you concern, then call the police immediately. Look out for anything that seems out of place, we would rather investigate concerns which come to nothing, rather than hear an incident could have been prevented.'