It's been said by some (ironically) unionists that any government involving the National party would be illegitimate given that not everyone in the United Kingdom has a chance to vote for them, and that such a government mightn't have won the popular vote, and England wouldn't stand for it, and the largest single party automatically gets to form the government, and Alex Salmond is a BASTARD and IT'S JUST NOT FAIR.
With that in mind, let's look at some figures.
In the 2010 General Election, not a single elector cast their vote for a coalition government comprising the Conservative party and the Liberal party.
Gordon Brown was prime minister in 2010 simply by being appointed leader of the Labour party in 2007. The electorate voted overwhelmingly for a Labour manifesto which was predicated on an explicit promise of Tony Blair serving a full term. Nobody was permitted to vote on Gordon Brown as prime minister (and at the first opportunity, he was slung out, with Labour coming in as the second largest party, and still trying to remain in power via a deal with the Liberals).
In the 2005 General Election, the Conservatives won the popular vote in England, defeating the Labour party, whose nominee for prime minister, one Tony Blair, clung onto office.
In the 2001 General Election, of the 659 seats in the House of Commons, the victorious Labour party contested only 640 (the Liberal party contested only 639). It was considered in 2001 quite legitimate that the good people of Glasgow (Springburn) and of the north of Ireland should be governed by the Labour party without having had the opportunity to vote for a Labour candidate.
John Major limped into the 1997 General Election governing without a Commons majority and relying on the support of the nine Ulster Unionist Party MPs to carry on, with a vote on closing mines only won after offering £10m concessions for industrial electricity users in the north of Ireland. In a previous vote, UUP MPs voted with Major after being promised an interconnector to Scottish Power.
If all of those governments are illegitimate (and if Labour, coming second in England, governing with SNP support is illegitimate, then so must they be), can I have all of the taxes I've paid since the 1997 General Election back, please?