At 1.27 on a Baghdad afternoon, Mr Blix gets down to work

They came armed with industrial vacuum cleaners and notebooks, and carrying with them the last flickering hopes that a calamitous war may be averted between the United States and Iraq.

Three years, 11 months, three weeks and five days after the United Nations withdrew its weapons inspectors from Iraq – the trigger for Britain and America to unleash a further onslaught on the country – another UN team arrived yesterday in what is seen as the final chance to stop a new war.

The return of the chief weapons inspector, Hans Blix, with 30 monitors was, in every sense, an historic occasion. But there was an immediate reminder of the constant conflict in the background. Even as the UN flight was landing at Baghdad, US and British jets were, for the second day running, attacking Iraqi air defences in the no-fly zone. The bombs are clearly part of the softening-up process on Iraqi defences before a military campaign to topple Saddam Hussein.

On his arrival, Mr Blix declared that the new search for weapons of mass destruction would give President Saddam a "new opportunity'', making it clear that there would be no more room for prevarication.

"Let me tell you that we have come here for one single reason and that is because the world wants to have assurances that there are no weapons of mass destruction in Iraq,'' he said. "The situation is very tense at the moment, but we are offering new opportunities, and I hope we can take these opportunities together. A question of war and peace depends on Iraq as well as the Security Council and members of the Security Council.''

Before boarding the flight at Larnaca in Cyprus, Mr Blix, 74, a former Swedish minister for foreign affairs, warned that nothing would be off-limits, including mosques and presidential palaces.

Mr Blix, wearing a grey suit and vivid green tie, led his team towards Baghdad airport at 1.27pm. They were accompanied by security guards, surveillance specialists with de-bugging equipment, and four industrial-sized vacuum cleaners for their offices in the capital, which were abandoned in December 1998.

The chief inspector marched forward for a perfunctory handshake with Husam Mohammed Amin, head of the Iraqi National Monitoring Directorate, a body set up by the Iraqi regime to "help the inspectors'' but accused by them of doing their utmost to be a hindrance. "General Amin said he was glad to see us, but he was careful not to say welcome, and we did not say 'thanks for having us','' one of the UN personnel said.

The multinational monitoring group, all in suits, then walked over freshly painted slogans on the floor saying "Down with USA,'' "Long live our beloved Saddam'' and "Up our Saddam'' for checks on their paperwork. They did not, they said afterwards, offer themselves for normal immigration or customs procedures.

Saddam Hussein International Airport, garishly lit and normally eerily empty, was packed with reporters for the much-heralded arrival of Unmovic (the UN Monitoring, Verification and Inspection Commission). They were overwhelmingly Arab – the Iraqi authorities have allowed in only a minuscule number of Western journalists, so far, for inspections which, they had declared, would take place in the full glare of publicity.

After a chaotic press conference, with Mr Blix swatting back hostile questions from Iraqi journalists, the party left in a mixture of Iraqi Mercedes limousines and white UN four-wheel-drives.

The inspectors were driven to their temporary residence, al-Rashid Hotel, where they did some further walking over the "American enemy", this time the face of George Bush Snr, painted on the entrance floor. The lobby had had its number of President Saddam pictures augmented overnight, from the normal six to 21.

The lift, going up to their rooms on the 13th floor, repeatedly stopped and, at one stage, started descending. "Is this the first material breach? [of the UN conditions]'' asked one weary member of the party.

In the afternoon the monitors made their first visit since 1998 to the Canal Hotel, their former headquarters, and the scene of several confrontations with Iraqi officials in the past. The blue and white building was being spruced up, a new UN flag has been hoisted, and the small garden at the front had had the flowerbeds weeded and the grass mown.

Mohammed al-Baradei, the Egyptian director of the International Atomic Energy Agency, accompanying Mr Blix, said the team was coming with details of suspect sites supplied by American and other intelligence agencies. "We have a very good game plan,'' he said.

Mr Blix and Mr Baradei held their first meeting with Iraqi officials last night. The initial tasks of their team would be to come to an agreement on how the inspections would be organised, and to set up the infrastructure for them to take place. More monitors are due to arrive on 25 November and formal inspections will begin two days later. In the long term, a force of more than 300 from 48 countries will be deployed. Mr Blix said some would be Arabs, though their numbers will be limited because Arab countries had failed to nominate candidates.

The UN has always maintained that it was driven out of Iraq by obstruction and intimidation by the Iraqi regime. In turn it was accused by the Iraqis of fabricating evidence and spying on behalf of the American and Israelis.

But, in their time, the inspectors found and destroyed 48 Scud missiles, 40,000 chemical munitions, 690 tons of chemical agents and 3,000 tons of chemical precursors. This time they will have to hunt for the so-called weapons of mass destruction across Iraq's 166,800 square miles, much of it difficult terrain. About 1,000 sites are on the inspectors' list; 100 are top priorities.

But for those returning, it was a time for nostalgia as they pointed out the changed cityscape, with new buildings and roads constructed in the last few years.

Ewen Buchanan, an Unmovic official, said: "It will take us a while to get set up ... We do know from past experience that one has got to be absolutely thorough. It will be up to the Security Council to decide whether or not Iraq has fulfilled its obligations and war can be avoided.''

But most people in Baghdad believe that the point of no return has already been passed. Watching the UN convoy whiz by, Salim Nasrullah, 29, an engineer, said: "All this means nothing. The Americans have made up their mind to attack us whatever we do. We are used to seeing our own people drive around in big cars, and this today may prepare us for seeing Westerners doing the same if the war goes badly.''