Olympia opened in 1886 in Hammersmith and Fulham as one of the great Victorian exhibition halls, an iron-and-glass cathedral built for commerce, circuses, and crowds. The Daily Mail launched its Ideal Home Exhibition there in 1908, and by the 1970s it was a fixture of the London spring: three weeks of show kitchens, model bungalows, central heating salesmen, and visitors with carrier bags full of brochures. Children rode the demonstration escalators. Pensioners came for the tea and the chance to dream about modernising the boiler. The crowds were thick, family-heavy, and unsuspicious. The litter bin where the bomb was placed sat in a high-traffic area. According to one unconfirmed report, a man in his twenties was seen leaving a package there shortly before the blast.

The Provisional IRA had developed, by 1976, an established protocol for warning calls before commercial bombings. A coded phrase, recognised by police, would give an approximate location and timing so the area could be cleared. At Olympia, police said they received no such warning. The Sunday Mirror's Manchester office reported a phone call from a caller identifying himself as the IRA's Irish Brigade, claiming responsibility after the fact. The BBC received a similar call. A later report on the BBC's Nationwide programme suggested the device had used a type of explosive hardware the IRA had not previously deployed in Britain, which may explain the absence of warning: the perpetrators were testing something, and warnings would have compromised the test. Olympia changed its security practices afterwards. So, quietly, did every other large exhibition hall in the country.

The Olympia bombing came near the tail end of a phase of the Provisional IRA's English campaign that had been running, on and off, since 1973. The pattern was relentless: pub bombings in Birmingham and Guildford in 1974; the Hyde Park and Regent's Park bombings still to come; a long succession of letter bombs, package bombs, and car bombs aimed at causing economic disruption and political pressure. By the late 1970s the campaign was beginning to slow. Wikipedia notes that in the period after Olympia, IRA activity in Britain dropped off significantly. This was not the end of the Troubles; the worst bombings of the campaign, including Brighton in 1984 and Manchester in 1996, were still in the future. But for a few years after that Saturday afternoon at the Ideal Home Exhibition, the litter bins in London's public buildings were searched more carefully, and the crowds came back.

Olympia is still standing. The Grand Hall, with its glazed barrel-vaulted roof, hosts the London International Horse Show every December, the Ideal Home Show every March, BBC Good Food shows, and book fairs. A multi-billion-pound redevelopment, announced in 2017 and continuing through the 2020s, is wrapping the old halls in hotels, a theatre, and offices, opening up a piece of Hammersmith that had stayed inward-looking for over a century. There is no plaque marking 27 March 1976 in the public areas. There rarely is at the sites of attacks like this; the work of memory falls to families and historians. Rachel Hyams is buried in north London. She was 79. She had gone, that afternoon, to look at houses.

Olympia sits in the dense Edwardian street grid of Hammersmith and Fulham, west London, with the Hammersmith and City line running along its northern flank. The Grand Hall's glazed roof is easy to spot from the air, set back from Hammersmith Road; Earl's Court, until its demolition in 2014, was the larger exhibition centre just to the south-east. Heathrow's eastern departures pass overhead at 4,000 to 6,000 feet on a daily basis.