The wrecking of the world's greatest steeplechase was the climax to 10 days of disruption, in which the Provisionals have thrown the national rail and motorway systems into chaos.
An estimated 20,000 people were stranded in Liverpool when their cars and coaches were marooned inside the racecourse. With most of the city's hotels full, it meant a night in emergency accommodation.
Merseyside's town halls and police joined forces, providing hot meals and shelter for those unable to get home.
The 100 horses left at the Aintree course during evacuation were rescued after four hours after the RSPCA and racecourse officials persuaded police to let them be removed.
The IRA's action was bitterly condemned by politicians of all parties as well as by owners, trainers, jockeys and racing fans, thousands of whom had travelled to Liverpool from Ireland as well as from all over Britain.
"I am appalled that the IRA seems to be threatening hundreds of thousands of people and causing such disruption," John Major said. "This is further demonstration of their contempt and disregard for the lives and interests of ordinary people."
The Labour leader Tony Blair said he was "horrified". "The Grand National is a tremendous sporting event," he said. "It has been deliberately ruined by a cynical terrorist act, perpetrated by people whose intention is to introduce terror into the election campaign."
The Irish Prime Minister John Bruton said last night: "Have the leaders of the Republican movement stopped to think how their actions will make Irish people all over the world feel this evening?"
The ease with which such a great sporting event was ruined is likely to mean extra security at this afternoon's Coca-Cola Cup Final at Wembley where a near capacity crowd of 75,000 is expected to see Leicester City play Middlesbrough. "Obviously we are asking everybody to be extra vigilant," said Martin Corrie, a Wembley Stadium spokesman.
At Aintree yesterday, jockeys were preparing to mount and some horses were already in the paddock for the 3.45pm start when the warnings were broadcast over the public address system. As thousands streamed away in what was probably the largest mass evacuation in the history of sport, bomb disposal experts carried out a series of controlled explosions around the Aintree stands.
The Princess Royal was taken to safety by Special Branch officers. Labour frontbenchers John Prescott and Robin Cook and Hollywood actor Gregory Peck, celebrating his 81st birthday, were also at the race.
Trainer Jenny Pitman broke down in tears as she described how she had to abandon her horses. "These people are lunatics. We must not give into them," she said.
Last night bookmakers were waiting to hear whether the race could be run on another day before deciding whether bets would stand. Malcolm Palmer, of Corals, said bets would be valid if the race took place tomorrow, unless a refund was requested.
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