The 31-year-old – named as Bradley Baker, from Suffolk – was discovered collapsed in Paradise Lane, off Norfolk Street, at 2.45am on Tuesday.

Nearby shop and taxi firm workers, who arrived for work on Tuesday to find the popular cut-through to the bus station cordoned off by police, spoke of their shock at hearing news of the death – though some said they feared it was a reflection of late-night violence afflicting the town and beyond.

Police have made a number of arrests and yesterday continued to question a 24-year-old local man, having obtained a warrant of further detention from town magistrates.

Mr Baker was taken to Lynn's Queen Elizabeth Hospital after being found injured but died there at 2pm the same day. Police said his family were at his bedside and are now being supported by family liaison officers.

Leading the inquiry, detective chief inspector Neil Firm said Mr Baker died despite receiving "the best possible treatment".

He added: "We know the victim spent some of the evening prior to the assault in Chicago Rock Café in Norfolk Street and then visited a take-away.

"We are urging anyone with information which may help our inquiries or who witnessed the incident or anyone fleeing the scene to contact us at the earliest opportunity."

When Mr Baker died, police immediately changed their inquiry from one of grievous bodily harm to murder.

Three men had been arrested close to the spot where Mr Baker was initially found, but they have all now been released without charge.

Another man – a 26-year-old local – was released on police bail on Wednesday pending further inquiries.

Forensic teams worked in Paradise Lane for much of Tuesday, but it is now open again and there is nothing to hint at what went on there.

Cheryl Edwards manageress at nearby Silver Spoon Cafe and Restaurant said: "It is a shock especially when it happens just down the road from where you work, but I have heard of a lot of fighting etc in the town.

It is a big concern and puts me off going out. I know a lot of people prefer not to go out now."

Workers at Norfolk Street taxi firm Capital Cars, who did not want to be named, said they witness much late-night violence in the town.

Mrs Julia Steinfeldt, owner of Woodentops furniture store next to Paradise Lane, said: "It was a shock to hear somebody had been so badly hurt. There has been trouble along here before but it is the first time somebody has really been hurt."

Police have widely promoted the success of a project billed Nightsafe, launched in Lynn last year, which aims to make streets safe for revellers through increased officer presence and partnerships with landlords.