They are often the ones in the firing line when trouble starts brewing on a night out.

Eastern Daily Press: Steve Fiske and Mike Lorenz at The Whalebone Freehouse pub in Norwich. Picture: SIMON FINLAYSteve Fiske and Mike Lorenz at The Whalebone Freehouse pub in Norwich. Picture: SIMON FINLAY

But while many city pubs are experienced at monitoring behaviour at the bar, one thing is harder to control – just how far potential troublemakers may be on the way to getting drunk before even setting foot inside.

Pre-loading, as it is known in the trade – people drinking alcohol at home, before going out to pubs and clubs to consume more – is now the thing many Norwich landlords most fear.

While experienced pub managers have strong systems in place to monitor how much people have had while inside their premises, the amount punters may have had to drink at home beforehand is a dangerous unknown.

It poses a tricky problem for bar staff and doormen across the city, who cannot tell how far someone is on the way to being badly drunk and find it is certainly something that is harder to police.

Eastern Daily Press: The Plasterers Arms in Cowgate. Picture: SONYA DUNCANThe Plasterers Arms in Cowgate. Picture: SONYA DUNCAN (Image: Archant Norfolk Photographic � 2011)

Today, some of them are calling for tougher rules and regulations – both on individual troublemakers in the form of police sanctions and the establishments selling booze – to prevent it from happening.

Many believe supermarkets have a moral duty to sell responsibly, while others think rival pubs should warn each other of dangerous individuals and that repeat offenders should be given a blanket city-wide ban.

Some however revealed that they feel they are between and rock and hard place of wanting to be tough on troublemakers, but also needing to attract customers and be fair and proportionate.

'The biggest problem is not knowing what we've sold them but knowing what they've had prior to coming in,' said Mike Lorenz, owner The Whalebone Freehouse in Magdalen Road.

Eastern Daily Press: Steve Fiske and Mike Lorenz at The Whalebone Freehouse pub in Norwich. Picture: SIMON FINLAYSteve Fiske and Mike Lorenz at The Whalebone Freehouse pub in Norwich. Picture: SIMON FINLAY (Image: Archant)

'A lot of people are picking things up from supermarkets and then hitting the pubs pretty loaded.

'That's the very difficult part which is tricky to police. You certainly can't breathalyse people as they walk in.'

Mr Lorenz said workers at The Whalebone 'try to take a responsible attitude of what we sell them', adding: 'If someone is becoming a bit too noisy or starting to affect someone else's enjoyment, we'd pretty clearly point it out to them.'

But he said having to confront someone about their behaviour is a 'dreadful scenario' and 'probably one of the worse things we have to face'.

Thankfully he said those problems are rare at The Whalebone – but that it is much better to prevent it happening at all.

'If you've got people moving from place to place, you never know where they're going,' he explained, adding that bar staff should alert nearby premises if they see potential troublemakers heading in their direction.

But he also said he wanted to see 'police and magistrates able to exercise powers on those that continuously break the law – that would be useful for everyone'.

James Linder, landlord at The Eagle in Newmarket Road, Norwich, agreed – adding: 'I don't think the repercussions on repeat offenders are strict enough.'

While sympathising with the limited resources of the police, particularly on a Saturday night when many resources are concentrated in the Prince of Wales area, Mr Linder said: 'We need to know the back-up is there.'

However he also believes: 'There needs to be regulation higher up and more control of the supermarkets selling alcohol.

'The biggest problem we've got is that supermarkets are offering such cheap booze deals.

'People are at home, pre-loading on alcohol with no idea how much they're consuming – there's no regulation there.

'They're then heading out into the city – they've probably had what they should've had already.

'I'm a firm believer that if you've got 10 people being rowdy, yes it might look good that you've got a full pub but that could put off another 20 people from coming in.

'You've got to think long-term. You've got to be in control of your pub.'

Craig Maskell, general manager of the Plasterers Arms in Cowgate, Norwich, said: 'People are getting pre-loaded – it's a shame.' He added that it is often difficult to spot because: 'Everyone deals with booze in completely different ways.

'Some people can have two pints and start to slur and sway.'

Part of the Plasterers Arms' solution, he said, is in the type of venue it is – as a pub for discerning beer drinkers, it attracts fewer heavy drinkers.