THERE's an amusing spoof history documentary on Scottish Labour leader Jim Murphy circulating at present on YouTube.

I'm quite sure an equally hilarious one could be done about Alex Salmond, or indeed many leading Westminster figures.

Mind you, given that footage showing quips from actual Alex Salmond public meetings are being tweeted by the Prime Minister as evidence of sinister intent, one suspects the entire campaign has had a massive humour by-pass.

But history is being wielded as a campaigning tool as never before, often with a complete disregard for accuracy. I will mention a few examples. No doubt The Herald's alert and notoriously well-informed readers will correct me but, in that event, I pledge, unlike politicians, not to keep repeating any porkies regardless.

It started with the Budget, which most observers regarded as the unofficial starting gun for the General Election campaign. There, George Osborne pledged one million pounds towards commemorating the Battle of Agincourt, which he said was well worth the money to mark the historical moment when "a strong leader defeated an ill-judged alliance between the champion of a united Europe and a renegade force of Scottish nationalists".

Factcheck: The victory by English and Welsh archers under Henry V was against French forces commanded by Charles d'Albret. French King Charles VI was in no champion of a united Europe, as he was too feeble to take part himself, and no Scots were involved. Perhaps Mr Osborne was mixing this up with the Battle of Bauge six years later in 1421, when Thomas of Lancaster lost heavily to mainly Scots troops led by the Earl of Buchan.

Then we got Mr Osborne's boss abandoning his usual smooth-cheeked demeanour to become Mr Angry on the Andrew Marr show, including this nugget: "This would be the first time in our history that a group of nationalists from one part of our country would be involved in altering the direction of our country, and I think that is a frightening prospect."

Where to begin with this argument? Given that Tories seem to spend all their time logging every joke made by Mr Salmond on the campaign trail, you might have expected them to notice that the former First Minister's most recurring trope has been to quote Irish Nationalist Charles Stewart Parnell: "No man shall have the right to fix the boundary to the march of a Nation. No man has the right to say to his country, 'Thus far shalt thou go and no further'."

So you might expect a UK Prime Minister to be familiar with the events from the time of Gladstone, when Mr Salmond's hero Parnell was a major player on the Westminster stage, even prompting a notorious forgery to discredit the Nationalist leader.

Or perhaps we might expect the Prime Minister to be familiar with December, 1910, when Herbert Asquith, from his East Fife constituency, sought to rule with the support of John Redmond's Irish Nationalists, although Conservative Arthur Balfour won the bigger share of of the popular vote and only one seat fewer than the Liberals.

Mr Murphy really needs his own lesson in the unwritten constitution of the UK as he has repeatedly, and falsely, claimed that the party with the most seats gets to form a government, when a string of experts has pointed out that it is the party that can form a majority coalition that can govern.

As for non-English influence, in 1974 Ted Heath built his approach to wooing the Liberals on the fact that he already had the Ulster Unionists in his pocket. Incidentally, that same year Kingsley Amis wrote in the London Evening Standard that Tony Benn was the most dangerous man in Britain, an accolade only now taken by Nicola Sturgeon, who has been given the John Major treatment of being deemed a "clear and present danger" - this from a man who opened negotiations with the IRA and had to rely on Ulster Unionists when facing the "bastards" within his own party.

But Ms Sturgeon is not immune to historical revisionism. When she talks of the impossibility of doing any deal with the Conservatives, she chooses to forget her time as Deputy First Minister in the 2007-11 minority Holyrood Government when, in order to get her party's budgets through, her Finance Secretary John Swinney had to rely on Conservative support.

The history lesson? When politicians cite historical precedent, go and look at the facts for yourself. Politicians play fast and loose with the past.