President Mobutu Sese Seko's soldiers, who had spent the morning blocking and bludgeoning Mr Tshisekedi's supporters, let him pass. One detachment - led by Kongolo "Saddam Hussein" Mobutu, the president's son - even began clearing a way to help him through. Heartened by this display of reconciliation, the crowd cheered louder still. Then, only 300 yards short of his goal, the trap was sprung.
As a fresh barrage of tear gas flooded the street, armoured cars screamed through the panicked crowd, pouring automatic fire into the air. The Prime Minister-designate staggered gamely on for a few yards before he was grabbed by soldiers and bundled into a car. His parade was over, and he never even made it to work. Having dabbled with democracy and reform, President Mobutu is reverting to a style of rule he seems more comfortable with.
On Tuesday night, while rebel forces were bombarding the southern city of Lubumbashi, Mr Mobutu declared a state of emergency and appointed senior officers to govern the five major regions still in government hands.
Yesterday morning, as Lubumbashi fell, government troops in the capital, Kinshasa, were using tear gas, rifle butts and batons to give Mr Tshisekedi's supporters a demonstration of what this state of emergency meant in practice. From the time they left their leader's house until the final rout three hours later, the crowds were subjected to repeated assaults at the hands of Mr Mobutu's troops.
The unrest marked the end of a long week for Mr Tshisekedi, nominated as Prime Minister by the parliamentary opposition just eight days ago. Initially, Mr Mobutu's followers agreed to the move, hoping to use the veteran democrat as a diplomatic foil to Laurent Kabila's advancing rebels. Just one day later the Prime Minister-designate announced he planned to dissolve the unelected parliament and prepare for elections, meanwhile appointing an interim cabinet that contains no Mobutist ministers.
Terrified at what amounted to a non-military coup, Mobutu supporters announced last weekend that they would no longer support Mr Tshisekedi as Prime Minister. On Monday and Tuesday, opposition students took to the streets to prevent MPs from making good their promise to sack Mr Tshisekedi. Yesterday, flushed with success, they were to escort their candidate to his first day at work.
So at 10.20am a procession of several thousand young men left the Prime Minister's house, waving the palm leaves that symbolise victory in Zaire. Less than 10 minutes later they were given their first taste of tear gas and rifle butts.
Foreign journalists were singled out for particular attention throughout the day. In the first attack a television cameraman and photographer were seized by soldiers, beaten up and robbed of their equipment. Later, as gunfire echoed over Mandela Roundabout, Zaireans were appealing for the foreign media to bear witness to their country's shame.
"You see how democracy is in Zaire," said Michel Chel-K, a member of Mr Tshisekedi's Democratic Union for Social Progress. "There is the legal Prime Minister in the street and they gas and shoot at him. Kabila should come now."
Early in the afternoon President Mobutu used emergency powers to appoint a new prime minister, General Likulia Balongo. With his supporters dispersed and the army in control of the streets, Mr Tshisekedi was released and sent home.
Yet the biggest loser in yesterday's street battles will be Mr Mobutu himself.
The United States yesterday stated that Mr Mobutu, its long time ally, should step down, and indicated it is trying to arrange a place of exile for a man the White House said was about to become "a creature of history".
The message was the clearest sign so far - and perhaps the decisive one - that the ruler who took power 32 years ago with the support of the CIA has now been irrevocably abandoned by his erstwhile Western patrons. Washington's goal now is a peaceful transition to democratic elections and a properly representative government.