In the early 1970s, an IRA man was shot at the wheel of his car. The car crashed into a family, the Maguires, and killed three of its children. Subsequently the mother, Anne, tried repeatedly to commit suicide, and finally succeeded. Mairead, her sister, married the widower, Jack.
Ms Williams, whose mother was a Protestant and father a Catholic, witnessed the accident. This prompted her to join forces with Ms Corrigan, a Catholic, to found the Peace People. The Norwegian committee's citation said: 'Their initiative paved the way for the strong resistance against violence and misuse of power, which was present in broad circles of people.'
Having picked up the Nobel prize cheque, the two declared the money would be channelled into the movement. But they began falling out over policy - Ms Corrigan wanted laws changed, Ms Williams said criminals must be punished. The years passed, Ms Williams moved to America and married an oilman. The peace movement, already in decline, saw its demise accelerated by the rift.
Ten years on, in 1986, a television documentary sought to bring the two together. They refused to appear together. Ms Williams admitted she had kept the Nobel money herself, saying she had worked hard for it.
On the face of it, the story of Ms Corrigan and Ms Williams had everything to captivate the worthy, progressive Scandinavians charged with dispensing Alfred Nobel's legacy in the modern age. Not only were they, like yesterday's laureates, credited with seeking to unite a divided community; they were ordinary people and, to boot, women.
But their individual story also brought home the risks of awarding peace prizes before the bigger story is over. Another example was Vietnam. It was a duo then, too, and probably the most notorious blunder committed by the Nobel committee in its 92-year-history.
Henry Kissinger and Le Duc Tho, the North Vietnamese foreign minister, were awarded the prize jointly in 1973 for 'negotiating an end to the war in Vietnam'. Dr Kissinger's prize led to the resignation of two committee members.
Tho refused to accept his on the grounds that there was no peace in Vietnam. Others objected that Tho had been known since 1930 as a hardline founder of the Indo-Chinese Communist Party. The war continued for another two years, and Dr Kissinger's Paris 'accords' were later discredited as a face-saving formula to allow the US to withdraw its troops from Vietnam. Tho died in 1990, his last years having been clouded by charges of being excessively pro-Chinese.
Peace duos were something of a Nobel craze in the 1970s. Menachem Begin and Anwar Sadat got the prize in 1978 for 'contribution to the two frame agreements on peace in the Middle East, and on peace between Egypt and Israel, which were signed at Camp David on 17 September 1978.'
Although Begin was more known as a warhorse than a peace-maker, most agree the prize was probably right for its time. 'Anyway,' said one veteran insider, 'it's always the old warhorses who end up making peace.'