From 1959 to 2010 Labour could be sure of one thing. It would win the majority of Scottish seats in a general election. It never won 50 per cent of votes cast, for there were parts of the country which never elected a Labour MP, but in the cities and across the central belt Labour was dominant. Labour Governments with small majorities – in 1964, 1966 and 1979 – were made possible by the party’s control of Scotland. So important was Scotland to the party that it was frequently said that, if Scotland became independent, there would never be another Labour Government in England.

Labour’s dominance in Scotland has melted, like snow off a dyke in a thaw. This was in part the consequence of economic change, the decline and then virtual disappearance of heavy industry and the weakening of trade unionism. Even so, the increase in the number of white-collar public sector jobs went some way to compensate for this.

At the same time the unpopularity of Thatcher Toryism led many in the established professions – the Law, the Church, Medicine, the Universities and the Civil Service – to vote Labour, a drift that was also reflected in the greater diversity of Labour candidates.

In the Labour landslide of 1945, few Scottish Labour MPs had university degrees. They were foot-soldiers, not officers, at Westminster and were rare birds in the Attlee and Wilson Cabinets. This changed. Scottish Labour MPs such as John Smith, Donald Dewar, Robin Cook and the young Gordon Brown kept the party on an even keel when it seemed in danger of moving so far to the Left as to be unelectable. When Labour at last won again in 1997, this time with a commanding majority, Tony Blair’s Cabinet was packed with Scots. Scottish Labour dominated British politics to such an extent that Andrew Neil wrote about “the Scottish Raj”. It even looked as if Labour had, thanks to Scotland, become what Harold Wilson had prematurely claimed it was: the natural party of government.

Yet, within twenty years, Labour’s support collapsed in Scotland. In 2015 it won only one Scottish seat, in 2017 seven, all but one with slim majorities. What had gone wrong? During the eighteen years of Tory Governments – Labour’s long years in the wilderness, 1979-97 – Scottish Labour committed itself, irrevocably, to devolution and the establishment of a Scottish Parliament. There were two reasons for this: first the determination that a Tory government with little electoral support in Scotland should never again impose Tory policies on domestic Scottish affairs; second the belief that devolution would be enough to halt the rise of Scottish Nationalism.

As Shadow Secretary of State for Scotland in the last years of John Major’s Government, George Robertson rashly declared that devolution would “bury the SNP”. Few heeded the warning from the veteran backbencher, Tam Dalyell, that on the contrary, it would put Scotland “on a motorway to Independence with no exits”.

The devolution legislation provided for a dual system of election to the Scottish Parliament. MSPs, 73 of them would be elected by the first-past-the-post system, 56 from party lists, every elector having two votes, one for the individual constituency, one for a regional list.

This apparently generous concession by Labour (which regularly had around two-thirds of Scottish seats at Westminster) was necessary if the Liberal Democrats and the SNP were to campaign for a Yes vote in the devolution referendum that took place in 1997. Neither would have supported a scheme which seemed likely to guarantee a permanent, or at least long-lasting, Labour majority in the new Scottish Parliament. With their support, the referendum was comfortably won, with only the Tories opposing devolution, and the first two governments in 1999 and 2003 were indeed Labour/Lib Dem coalitions.

Then in 2007 the SNP emerged as the largest party, only a few seats short of a majority in the Parliament. It formed a minority government, which was deemed moderately successful, and then in 2011 won an outright parliamentary majority. So surprisingly, we had a one-party government.

This wasn’t supposed to happen, and had indeed been thought so unlikely as to be almost impossible. That it did come about pointed to a significant difference between Labour and the SNP.