It also brought back memories of attacks in Britain during the 1970s when pubs in Guildford, Woolwich, Birmingham, Caterham and Maidstone were blown up - although then there was loss of life.
Shoppers, tourists and office workers were walking in the sunshine in the narrow streets around The Sussex pub in Long Acre, where the bomb had been planted. Although it was half-empty yesterday, the bar which bore the brunt of the blast is often packed.
One of the five victims, a middle-aged man, suffered serious facial and neck injuries and later underwent prolonged surgery at University College Hospital. None of the other victims, also middle-aged men, was seriously hurt.
A warning had been given at 1.13pm, just nine minutes before yesterday's explosion next to Stringfellow's nightclub and 50 yards from West End theatres and the Garrick Club where many MPs are members. The warning, telephoned with the IRA codeword to a radio station, said only that the bomb was in 'the Leicester Square area'.
After the explosion yesterday, Commander George Churchill-Coleman, head of Scotland Yard's anti-terrorist branch, said the bomb was a small device, but big enough in the confined space to cause very serious injuries.
'This is now typical of the cynical disregard that the terrorist has for public safety and life, indeed people in general,' he said. He appealed to the public to remain vigilant to help minimise the number of bombings, but added: 'Whatever you do, do not be deterred from going about your normal business - that's what the terrorists want you to do.'
John Cracknell, 24, who was about 10 yards from the pub when the bomb went off, said: 'There was glass all over the pavement and some smoke coming out of the building. I ran in through the front door of the pub and downstairs to see if anybody was injured. The stairs were strewn with rubble.'
An arts student, Sef Townsend, 44, said he had been about to enter the pub at 1.30, but had stopped to give a tourist directions. 'If I had been three seconds earlier, I would have been in there,' he said. 'I went in and saw the carnage. The bar was completely destroyed and there was a man lying there. He looked very ill.'
The blast, and the seven London bombings last week, have raised fears of a prolonged autumn campaign on so-called 'soft' targets in mainland Britain.