No one who passed through Brighton and Hove this week could have failed to notice there was a big event on the seafront.

The city's main conference centre and neighbouring hotels were turned into a fortress and hundreds of police, many of them armed, swarmed all over the city centre.

Brighton was the first resort to enter the conference business in a big way following the decline of the fortnight-by-the-sea holiday trade. And it has paid off.

Thousands of people attend hundreds of conventions every year, making millions of pounds for the resort and its people.

While most of the money is spent in restaurants and hotels in the centre, there is a ripple effect that benefits others, ranging from flower sellers to taxi drivers.

Brighton and Hove City Council is so keen on conferences that, like many other resorts, it lets most use its main hall, the Brighton Centre, free of charge.

The council estimates the Labour Party conference, one of the biggest to visit Brighton, is worth about £5 million to the city directly.

There is also a big indirect benefit in the many mentions of the city in papers around the world and images projected on TV screens.

But The Grand hotel bombing in 1984, which killed five people at the Conservative Party conference and injured many more, changed the nature of political conferences.

Since that time, there has been enormous security for the conference of the governing party, whether it is Labour or Conservative.

The security costs, shared locally and nationally, come to more than £2 million each time.

After the atrocities in America on September 11, protection for Labour's conference was increased hugely, with measures never before seen in Brighton and Hove, including motorway-style crash barriers outside the main venues.

On Monday morning, people driving into the city from the west were taking more than an hour to cover a two-mile journey along the coast road and there were lesser delays on the other mornings.

Many people were deterred from coming into the city centre on Sunday by reports there would be a march by 10,000 people, with the possibility of violence. In the event, rain reduced the numbers and the protest was peaceful.

The conference was shortened by a day due to the international situation but council tourism head Amanda Shepherd said: "Most people packed four days' entertainment into three."

She said in spite of the obvious concern by everyone over the American tragedy, the event had been a success for the city, with just as many visitors as before.

Roger Marlow, chairman of the city's hoteliers' association, said: "It was a fabulous conference for Brighton and Hove.

"You couldn't pay for all this publicity. All these people come to the city and make it one of the country's best-known places."

Hotels were mostly fully- booked. Some delegates and visitors had to stay as far away as Eastbourne, Worthing and Gatwick so they could attend.

City centre manager Tony Mernagh said the conference was, as always, something of a curate's egg for Brighton and Hove.

He said: "It was very good for restaurants and hotels but pretty poor for retailers.

"September is not a strong month for retail and neither is the first bit of October. The Christmas rush does not really start until the school half-term.

"It's all swings and roundabouts. Most retailers know they may not make much money out of the conference but other sections of the local economy do and they are happy to accept it."

Labour council leader Ken Bodfish said the conference had, as usual, proved a boon to the hotel and restaurant business.

On Monday evening, he was in Terre A Terre in East Street which was packed with ministers, MPs and delegates.

Nearby Donatello, one of the city's biggest restaurants, was also full.

Tory Opposition leader Brian Oxley said: "We welcome anything that will bring more people to the city. It is good for local business.

"There are security considerations but, when you look at what is on offer with big political conferences, we have to put up with them."

Next year there will be less security when Brighton and Hove plays host to the Liberal Democrats and Labour head north to Blackpool.

But, despite the disruption, the city is already bidding to have Labour back in two years' time.