The date March 28, 1979, was arguably one of the most memorable and exciting Parliamentary nights of the 20th century. It was the night that James Callaghan's Labour Government was destroyed.
And by doing nothing, two Northern Ireland MPs played a crucial role in a vote which put Labour out of power for the next 18 years.
Gerry Fitt, then leader of the SDLP, and Frank Maguire, an independent republican, rejected the blandishments of the Government whips and abstained. The result of a vote of no confidence in the Government - a vote which ultimately put Margaret Thatcher in 10 Downing Street - was 311 to 310.
If just one of this pair had voted for the Government and created a tie, then the Speaker, George Thomas, would by convention have voted for the status quo, ie the Government, and Callaghan would have lived to fight another day.
Britain had just emerged from the Winter of Discontent, when a wave of strikes, including gravediggers, dustmen and other vital services, spelled misery for most and brought what amounted to terminal damage to the already unpopular Labour Government. In December 1978, the Government survived, by 10 votes, an earlier vote of no confidence. This was thanks largely to the Ulster Unionists who approved of legislation which would increase the number of seats in Northern Ireland.
By then, however, the Liberals had walked out of the so-called Lib-Lab pact and the Government was held together by a shoestring.
There were frantic discussions during the day of the vital vote. One Labour MP, Dr Alfred Broughton, was gravely ill and although he was willing to be brought to Westminster from Yorkshire for his vote to be recorded, Callaghan decided against doing that. Dr Broughton died a few days later, on April 2.
The conversations included abortive talks between Enoch Powell and the Ulster Unionists over a pipeline which would bring cheap energy to the province. Ultimately, some unionists voted with the Government and some against.
But the key problem involved Fitt and Maguire. Fitt was generally sympathetic to the Labour Government, but made a speech on that day to say he could not support it on this occasion because Labour had failed to grapple properly with the Irish situation. It was, he said, the unhappiest speech he had ever made at Westminster.
But he promised, if Labour were defeated, to campaign for Labour's return to office afterwards. This was a genuine promise, but it was cold comfort for Callaghan in his hour of dire need.
Maguire, although not an abstentionist MP, rarely came to Westminster. But he did on this occasion and was given a 'minder' in the form of a Labour whip, to make sure he did 'the right thing' when the vote was called.
But he did very much the wrong thing and, like Fitt, abstained. The Government whips were furious. Maguire had objected to the increase in the number of seats for Northern Ireland, a move which, he said, would favour unionists.
It is understood that Maguire kept the Government whips on tenterhooks for most of this dramatic evening, because he did not finally decide to abstain until the 11th hour. Apparently, his wife, having heard Fitt's contribution to the debate, urged her husband to do likewise.
As Roy Hattersley said at the time, this marked the death-throes of Old Labour. It was not until 1997, after 18 barren years, that Tony Blair led New Labour back to power.
Chris Moncrieff is a former political editor of the Press Association