Welcome to Fortress Brighton. For the next seven days the city will be in the grip of the most high-profile police operation in its history.

Yesterday, four days before the first delegate takes his place on the conference floor, the seafront road was gridlocked as cars queued to get past the rising barricade.

Barriers of steel encased in concrete will surround the Brighton Centre, the De Vere Grand hotel, the Russell Road car park and the Hilton Brighton Metropole Hotel, creating an island within the city.

Armed police have begun random checks on vehicles driving into the centre. They have powers to stop and search anyone they consider suspicious.

That includes shoppers, tourists and daytrippers.

They also have permission to close roads in the city at short notice.

A contraflow system will squeeze traffic on to the southern carriageway outside the Metropole Hotel after 7pm.

There will be no night access from Regency Square into Kings Road, while people living near the Brighton Centre will need vehicle passes to get to their homes via a checkpoint.

The £2.3 million cost of mounting the security operation, codenamed Otter, will be met from central government funds. The cost in lost business, lost trade, in the general hassle and delays will be felt locally.

Chief Superintendent Phil Clarke said while the counter-terrorist challenge was higher than ever, he was confident it would cause "as little disruption to the city as possible."

Others are not so sure.

The conference is undoubtedly a boon for hoteliers hit by the washout summer. Some 20,000 delegates are expected to spend up to £15 million in the city's bars, hotels and restaurants.

The summit also serves as a shop window to the conference industry which provides 13,000 jobs in Brighton and Hove.

But not every businessman has a hotel room or a seat in a restaurant and many see the conference as a hindrance as much as a prestige event Brighton should welcome.

Taxi driver Allen Bicks, 48, describes the conference, and specifically the fact that it is being policed by more than 1,000 officers, as "a charter for criminals".

He said: "I would rather it wasn't here, to be honest. It's not worth the aggro.

"It will create mayhem with the traffic."

He said: "The contraflow on the seafront will create traffic disruption all the way from the marina to Hove. People will use Western Road instead and that will become jammed.

"The Lib Dem conference was the last one I came across but no one notices when they are in town - all you get are a few more teachers bumbling about."

What about the effect of the conference on businesses?

Managers at the Odeon cinema, next door to the Brighton Centre, say customers are scared away by the armed police.

Marketing manager James Tully said: "There was a time when the whole cinema was shut down for the conference. That doesn't happen any more because it costs too much in the compensation they have to pay.

"Because we are adjoined to the Brighton Centre they come in and check.

"We have armed policemen patrolling the building which is enough to scare anyone off."

Mr Tully, like many businessmen and women working in the city centre, balances his disdain for the fuss caused by security with his pride that Brighton is the kind of modern, prestigious city which could cater for an event of this size.

Emilio Savvides, manager of the Regency restaurant, also sees marginally more benefits than disadvantages with playing host to the conference.

He expects to take £10,000 next week when normally he might expect £5,000.

He said: "The conference obviously brings business to the town. There is no doubt about that.

"It is the time of year when things go quiet for us on the seafront, so it is a bonus.

"The unreliability of the weather means we rely a lot on conferences like this once.

"But it slows down the traffic and people take longer to get to work. Some people that would otherwise come to us won't bother going to the seafront. It does affect business but that is compensated by the delegates."

The tentative welcome from business is echoed by the people who live and shop in Brighton.

Brighton and Hove City Council is wholeheartedly supportive. Civic leaders accept there will be disruption but believe it a small price to pay for the benefits.

A spokesman said: "It raises the profile of the city as a conference venue.

"Our conference industry is vital to the local economy as we have something like 13,000 jobs dependent on the visitor industry - tourism and conferences. Autumn conferences are very important in attracting visitors outside summer months, effectively extending the season."

People living near the conference have been advised of the security arrangements in pamphlets and most said disruption so far had been minimal.

But most do not have cars.

Then there is the threat from campaign groups which include the trade justice movement, pro-hunt campaigners, anti-war demonstrators and a sizeable crowd of football fans still patiently waiting for a decision on the Albion's Falmer stadium.