As the cars stopped at the traffic lights, preparing to turn right, a man standing outside the Karh Sports Club opposite stepped into the road and threw a grenade. He then ran towards the left side of the first Mercedes, firing his Kalashnikov machine-gun at the driver.
At the same moment, three other gunmen waiting in Mansur Street began to shoot at Uday's car and the two following, which were packed with bodyguards. By the time they had finished Uday had been hit by eight bullets, one of which is still lodged in his spine. Although he survived, Iraqis believe he is too badly crippled ever to succeed his father.
It was the most carefully planned assassination attempt in the Middle East since President Sadat of Egypt was shot dead 15 years ago. Now, one of the leaders of the group which carried out the attack says in an interview with The Independent - the first describing the assassination - how they tried to get close to Uday for two years before they finally succeeded.
Ismail Othman, a fresh-faced Iraqi in his late twenties now hiding in Europe, revealed that the attack was carried out by al-Nahdah (the awakening), a small group, mainly comprising former students from Baghdad. At first they considered kidnapping Uday. An earlier attempt to kill him at a farm he owned at Salman Pak outside Baghdad failed because he did not turn up.
The account of the plot given by Mr Othman, a code-name adopted to protect his family who are still in Iraq, can be partly confirmed by other sources.
But he gives many fresh details, such as the fact that Uday almost escaped because on the night of the assassination attempt he was not driving one of the Mercedes as he usually liked to do. He also says al-Nahdah suffered heavy losses in February this year when Iraqi security discovered where the group was meeting, when one of its members accidentally bought a stolen car.
Mr Othman says, as originally revealed by The Independent, that the key breakthrough for the attackers was when they acquired an inside source. He says: "We had a good contact with a member of the ruling elite from [Saddam's home town of] Tikrit called Ra'ad al-Hazaa."
A distant relative of the Iraqi leader, Mr Hazaa helped the assassins because of a family feud. He wanted revenge because in 1990 Saddam killed and cut out the tongue of his uncle, General Omar al-Hazaa, for criticising the regime.
Al-Nahdah, formed in Baghdad in 1991 in the wake of the uprisings after the Gulf War, had early decided that it was not feasible to assassinate Saddam himself. Even members of his inner circle in Baghdad do not know where he is. Film on Iraqi television of him addressing the ruling Revolution Command Council may be shots of a meeting which took place months before.
"We decided to kill Uday two years ago," says Mr Othman. "We thought the regime had four pillars: Saddam himself, Uday and his younger brother Qusai [head of security services] and their cousin, Ali Hassan al-Majid. Of these Uday was the easiest to get to."
Uday was also probably the most hated man in Iraq, with a reputation for using extreme violence. In 1988, at the age of 24, he was arrested by his father for beating to death Kamil Hanna Jajo, one of his father's bodyguards, during a party.
The real motive for the killing was that Jajo had acted as a go-between in an affair between Saddam and his mistress. Sajida, Uday's mother, took his side and after a week he was released from prison.
Operating from his headquarters in the eight-storey Iraqi Olympic Committee headquarters, a fortress-like yellow building in Baghdad with its own prison, Uday turned himself into his father's chief henchman. He ran an influential newspaper called Babil.
In 1995, at another drunken party, he shot his uncle Watban, a former interior minister, through the leg. This led his cousin, Lieutenant-General Hussein Kamel, one of his chief rivals for power, to flee to Jordan. When he returned, believing he had been pardoned, Uday killed him.
Since the Gulf War, Uday has built up a fortune through his control of smuggling, a highly profitable business since the Iraqi economy is isolated by United Nations sanctions.
The savage feuding within Saddam's extended family over the past three years gives an impression of anarchy in Iraq. In reality, the regime has never weakened. Iraqi society remains disciplined. There are few troops to be seen on the streets of Baghdad, though security police are everywhere.
The opposition has mostly fled to Iraqi Kurdistan or to Iraq's neighbours, where it has usually become dependent on foreign intelligence services.
It was an extraordinary achievement for al-Nahdah, dedicated to establishing democracy in a united Iraq, to have conspired successfully against the government.
It was tightly disciplined. It even survived the death of its general secretary and founder, Hamoudi Ali, an electrical engineer, who was captured and tortured to death by Iraqi security last year.
The success of the plot against Uday turned on some loose talk by one of his relatives and boon companions, Lu'ay Kharallah Tulfah.
In the past there had been no contact between those caught up in bloodthirsty feuds within Saddam's family and opponents of the regime. Suddenly, last December, the two streams came together.
Mr Othman says: "Over a drink in his home Lu'ay told Ra'ad al-Hazaa that he and Uday were planning a party in the al-Mansur district in three days' time."
Lu'ay clearly did not realise that Ra'ad, once an officer in Saddam's palace guard, now had dangerous friends.
The Iraqi elite, known as the "Tikritis", mostly come from Tikrit, a city on the Tigris north of Baghdad. It is at the centre of the Sunni Muslim Arab heartland of the country, though three-quarters of Iraqis are Shia Muslims or Kurds.
It was home not only to Saddam, but to an important member of his clan, General Omar al-Hazaa, an Iraqi army divisional commander in the 1970s. But when Saddam attacked Iran in 1980, starting eight years of war in which more than a quarter of a million Iraqis died, General al-Hazaa became critical. He retired from the army.
An Iraqi army officer, now in exile, says that in his cups at the retired officers' club in the Yarmuk district of Baghdad near his house, General Hazaa often expressed open contempt for Saddam's branch of the family. (It comes from the village of al-Ouja outside Tikrit and was not part of the traditional clan leadership.)
The officer says: "In 1990, the general was arrested. He was taken to al-Ouja and his tongue cut out. Then he was executed. His son Farouq was executed at the same time and the general's house in Baghdad was bulldozed."
When Ra'ad, the nephew of the dead general, learnt about the party Uday was due to attend in three days' time, he knew his moment for revenge had come. He told the al-Nadhah group whose members immediately started mobilising their military section. (The Iran-Iraq war and the Gulf War meant that most Iraqi men have military training and weapons are easy and cheap to obtain.)
Knowing the time and place of the party in al-Mansur, a fashionable district in west Baghdad, which Uday was to attend, made it easy to choose the site for the ambush.
"We thought Uday would have to take one of two routes to come to the party," says Mr Othman. "We chose a place where the two roads met at crossroads. It also had good street lighting in case it was dark when he arrived.
"We knew he would be in one of three white Mercedes, all the same shape, model and with the same number plates to confuse attackers about the car which Uday was in."
The would-be assassins decided to ambush Uday where Mansur Street, a long straight road, reaches Baghdad International Street (see map).
There are many shops in the area, so members of the al-Nahdah attack group standing in the street would not attract attention. Uday's convoy would also probably have to slow down at the crossroads.
Four men, all armed with Kalashnikovs and four clips of ammunition each containing 30 rounds, were positioned to attack Uday's car from the front and sides, whichever route he took.
Mr Othman says Uday was delayed because he had gone to feed his pet police dogs, as he did every Thursday, at the Jadriya boat club on the Tigris.
Just before night fell, the gunman outside the al-Karh Sports Club saw the first white Mercedes speeding up Mansur street.
Two other members of the ambush squad were waiting at the opposite street corner outside the Ruwad restaurant. A fourth man stood in a side street near the two getaway cars, ready to shoot at the second two cars in the convoy from behind to prevent the bodyguards helping Uday.
Everything went according to plan, except for one small error. Mr Othman says: "We believed Uday would be driving the first car because that is what he normally did. In fact, he was sitting in the passenger seat."
The gunman outside the Karh Sports Club, who was the first to shoot, concentrated his fire on the driver as originally planned. It was one of the men outside the Ruwad restaurant who realised that Uday was not sitting where he was expected. He saw him instead in the passenger seat and fired at him at almost point-blank range. A government official later admitted that Uday was hit by eight bullets.
"It all took one-and-a-half to two minutes," says Mr Othman. Then, three of the ambush party ran down Mansur Street to the two getaway cars, covered by a single gunman who was still firing at the convoy.
The escape had been carefully planned. The getaway vehicles each had number plates from a western Iraqi province least likely to be enemies of Saddam Hussein and therefore less likely to be stopped by the police.
Surprisingly, the government immediately confirmed that Uday was wounded, though not how badly. According to one source, this was to quell rumours that Saddam himself had been hit.
Mr Othman says those who planned and carried out the ambush escaped by travelling into Iraq's western desert, where they were joined by Ra'ad al-Hazaa, and finally reached Jordan. He says they chose this route because Iraqi security would expect the assassins to seek refuge in Iran or Iraqi Kurdistan, both only two or three hours from Baghdad.
Another Iraqi source has told The Independent the assassination group did enter Iran. The Iraqi government demanded they be returned by the Iranians. It is possible Iran insisted that the men who had tried to kill Uday deny that they had ever entered its territory.
Some members of al-Nahdah stayed behind. They remained undetected until 2 February when they held a meeting at al-Kreeat, north of Baghdad. Unfortunately, one of them had bought a car which turned out to be stolen. When security came to investigate, one of the guards at the meeting opened fire. Mr Othman says: "The soldiers used rocket propelled grenades to blow up the house over the heads of the 11 defenders. All of them were killed along with three Iraqi soldiers."
Uday recently left hospital on crutches, claiming he was recovering. He has not been seen since. Iraqi sources say he is too badly injured to regain his old power.
Mr Othman believes that by showing there was a real Iraqi resistance, which could strike at the leadership, the attack on Uday "achieved 100 per cent success".
Pillars of a savage regime
'We decided to kill Uday two years ago,' said Ismail Othman. 'We thought the regime had four pillars: Saddam, Uday and his younger brother Qusai [head of security services] and their cousin, Ali Hassan al-Majid. Of these Uday was the easiest to get to.'
Pictured, top, from left: Saddam Hussein and Qusai Hussein. Left: Ali Hassan al-Majid.Reuse content