One of the many ironies of the 2015 General Election was that the greatest beneficiary of our unfair first past the post system was one of the few parties that seriously wants it changed.

The SNP won 95 per cent of Scottish seats on 50 per cent of the vote. What madness is this?

Labour won 24 per cent of the vote, yet had the same number of seats, one, as the Scottish Liberal Democrats who had 7 per cent. The Scottish Conservatives had their worst election defeat in a century but still got the same number of seats as Labour.

And, of course, David Cameron became Prime Minister on just over 37 per cent of the vote. His government is now trying to outlaw strikes in essential service where fewer than 40 per cent of those eligible to vote support the action. On that criteria most of his MPs would be out on their ear and he'd possibly be sitting on the opposition benches.

But the worst UK losers from the General Election were Ukip. They won more than four million votes, 12 per cent, and got just one seat. According to the Electoral Reform Society which has condemned the 2015 election as the "most divisive" ever, they should by right have had 54 seats.

The Left used to quite like the winner-takes-all FPTP partly because it locked parties of the far left or the right out of parliament. Politics was seen as a class-based zero sum game - the workers versus the bosses, Labour versus the Tories.

FPTP used to marginalise the SNP too because its vote was widely spread. Labour didn't complain in 2010 when the SNP got only six seats on 20 per cent of the vote, while they got 41 on 42 per cent of the vote.

Indeed, in 1997, Labour won its greatest electoral landslide on far less than the SNP in 2015. Tony Blair won a majority of 179 on just 43 per cent of the vote. Few Labour people then complained.

The thing about FPTP is that once you do cross the 40 per cent threshold by a significant margin, you get just about every seat there is. This is what the SNP did in May, almost wiping Labour and the unionist parties off the map despite only getting just over half the popular vote.

I don't want to detract from the SNP's success however. Even under a proportional system, they would still have delivered a landslide - around 37 seats according to the ERS to Labour's 14.

The May result was astonishing precisely because it was so uniform. No area of Scotland was untouched by the SNP advance - the Highlands, Borders, Tayside, Central Belt, North East, West Coast. It was a remarkable result even under FPTP

Labours's apparent enthusiasm now for electoral reform may not be unconnected with their destruction in Scotland. I was taken to task on Twitter recently for saying this and told that Labour has "always supported electoral reform". Well, in principle perhaps, but it never did anything about it in Westminster when it had the chance.

Tony Blair promised the Liberal Democrats he would introduce proportional representation after his landslide in 1997. But somehow having a three-figure majority on less than half the vote was just too good to give up. He set up the Jenkins Commission on the voting system, read its recommendations and then ignored them.

Arguably, we would not have had the Iraq War if he had listened to Jenkins' call for a proportional system. It was only Mr Blair's inflated majority that allowed him to see off the biggest backbench rebellion in his Labour's history - and a march of more than one million people in London.

The Liberal Democrats in coalition with the Tories after 2010 managed to secure a referendum on the Alternative Vote system. But this was rejected largely because the AV system, though fairer at constituency level, does not lead to proportional representation in the UK parliament.

Only the Single Transferable Vote system, that we use for local government elections, or Holyrood's Additional Member System, ensures the number of seats in the legislature represent the votes cast for each party.

It works pretty well. Indeed, one of the reasons Holyrood is growing in authority over Westminster is because it is now seen as more democratic and representative of how people actually vote.

But be advised: there is zero chance of Mr Cameron reopening the fair voting issue in Westminster this parliament. It's his result and he's keeping it.