Seven horses of the Queen's Household Cavalry lie dead after the IRA detonated a nail bomb, 1982

The Hyde Park and Regent's Park bombings were one of the worst IRA atrocities on the British mainland, killing 11 soldiers and seven horses and injuring dozens.

Bombs were detonated within a few hours on July 20, 1982, and it was time for maximum casualties. Military casualties were quickly remedied. But the lens of the long-range camera captured terrifying detail, with the crumpled remains of a car bomb surrounded by dead horses.

Part of the power of the image is that it shows how indiscriminate the attack was. Soldiers were normally the primary target, but terrorists were willing to accept whatever collateral damage they did to them – including these horses. The dead and dying horses reinforce the brutality of the act and thus the power of the image.

These devices were involved in a series of IRA bombs that exploded in London over a period of four years, killing 20 people and injuring nearly 200.

The Hyde Park explosion caused particular outrage not only because of the human casualties but also the deaths of horses. Sefton, a horse that survived, was the subject of heavy media attention and came to be regarded as a national hero by many in Britain.

At 10:40 a.m., a nail bomb exploded in the trunk of a Blue Morris marina parked on South Carriage Drive in Hyde Park. The bomb contained 25 lb (11 kg) of gelignite and 30 lb (14 kg) of nails.

It exploded as soldiers from the Household Cavalry, Queen Elizabeth II's official bodyguard regiment, passed. He was participating in his daily Changing of the Guard procession from his barracks to the Horse Guards Parade in Knightsbridge.

Three soldiers of the Blues and Royals were killed outright, and another, their standard bearer, died of his wounds three days later. Other soldiers involved in the procession were badly injured, and several civilians were injured. Seven horses of the regiment were also killed or had to be euthanized due to their injuries.

Two hours later, a second bomb exploded under a bandstand two miles away in Regent's Park, killing seven soldiers with a Royal Green Jacket band. The bomb had been hidden under the stand for some time and was triggered by a timer. Unlike the Hyde Park bomb, it had no nails and appeared to have been designed to cause minimal harm to spectators.

The IRA claimed responsibility for the attacks by deliberately echoing the words of Prime Minister Margaret Thatcher when Britain entered the Falklands War a few months earlier. He declared that: "The Irish people have sovereign and national rights which no act or commercial force can exert".

Sefton, a horse that survived the attack at Hyde Park despite serious wounds, rose to fame after appearing in several television shows and was awarded Horse of the Year.

Sefton's rider at the time of the bombing, Michael Pedersen, survived, but claimed to be suffering from post-traumatic stress disorder; After separating from his wife, he committed suicide in September 2012 after killing their two children.

In October 1987, 27-year-old Gilbert "Danny" McNamee of County Armagh was sentenced to 25 years in prison for his role in the Hyde Park bombing and others in the Old Bailey, despite his plea that he was not guilty.

In December 1998, shortly after Maze was released from prison under the Good Friday Agreement, three Court of Appeals judges overturned his sentence, deeming it "insecure" because of fingerprint evidence implicating other bomb makers. He said that although the conviction was unproven, it did not mean that McNamee was necessarily innocent of the charge.