On March 26th 1979, the Callaghan Government lost a vote of no confidence by one vote. When was the last time that happened? - no idea, but a very long time ago.
Sir George's copy of the division list, signed by all Conservative Whips
Although the Labour Party won the October 1974 General Election with a small overall majority, it lost it through a series of disastrous by-elections; Woolwich West, Workington, Walsall, Birmingham Stechfield, Ashfield etc. When Wilson resigned and Jim Callaghan took over in 1976, he won some breathing space with the LibLab pact. David Steel and the Liberals gave him a two year guarantee of office.
Callaghan had a opportunity to call the Election in September 1978 but, for reasons which I didn't understand at the time and have never understood since, he didn't take it. He might have won.
By early 1979, the Callaghan Government was unpopular and the General Election was approaching. The Liberals were understandably reluctant to continue to prop up a failing administration and ended the pact. The Winter of Discontent in 1978/9 showed the Government to be at the mercy of trade unions, who brought the country to its knees with strikes in the public sector.
In March, the Government lost a vote on its handling of the economy and Denis Healey could be seen, after the vote in the Chamber, shouting at the leftwingers who had not supported their Party. Mrs Thatcher tabled a Motion of No Confidence for March 26th.
The rest, as they say, is history. I was in the Opposition Whips office at the time, and we took no chances. Colleagues were invited to check in by lunch time, but the arithmetic was never clear until 10pm. Frank Maguire, an Irish MP who was not seen very often, came over and was escorted throughout the day by Don Concannon, a large Labour MP. But he slipped his leash and "abstained in person". Rumours of a deal with the Welsh Nationalists came and went. And when Doc Broughton, an ill Labour MP, was not brought in on his sickbed, the Government went down by one.
After the vote was announced, Jim Callaghan said he would be calling on the Queen to ask her to dissolve Parliament. Labour MP's sang the Red Flag. The Opposition whips had a small glass of champagne, and prepared for Government.