WE ARE becoming accustomed in Scotland to the idea that the SNP are scaring the establishment at Westminster like barbarians at the gate.

The more the Tories' Australian hard-ball strategist Lynton Crosby sticks Ed Miliband in Alex Salmond's top pocket to bounce the English vote, the more the Scots seem to revel in their kingmaker role. The SNP have countered with one of Nicola Sturgeon in a business suit with both Cameron and Miliband in her pocket.

The point, calmly made by our columnist Iain Macwhirter yesterday, is that an ever-more sophisticated electorate North of the Border is entitled to vote, as the UK citizens we were love-bombed into being last autumn, as British voters who do not care for Conservative rule.

The row has manifested itself over issues such as the television debates, resulting in last night's curious indirect encounter between Messrs Cameron and Miliband, or armchair constitutionalist blustering about how the Scots should behave at the next General Election. Essentially, get back in your box and shut up.

It's not looking that way. In spite of the near desperate efforts by some in some sections of the media there is no sign that leader Nicola Sturgeon and her mentor Alex Salmond are singing from different hymn sheets. The SNP has always said, relentlessly, that when it falls short of its ambition of independence its aspiration becomes simply "the interests of the Scottish people." You might find their version of that presumptive or contrary to your own views, but that's what they say.

Which brings us to our story today about the broader impact on Westminster of the SNP potentially becoming the third biggest party at the Mother of Parliaments. There is political involvement at stake through Westminster procedures, and there is also hard cash.

As we report it has dawned on Westminster that under current rules should the SNP reach a tipping point at the General Election and secure upwards of forty seats there will be hard cash involved and far greater procedural clout.

It would be fair to say Harold Wilson did not see this coming when he allowed his Leader of the House, Ted Short, to come up with the formula. "My Ministers will consider the provision of financial assistance to enable Opposition parties more effectively to fulfil their Parliamentary functions," said Wilson.

Little could the wily Labour leader have thought in 1974, even although the SNP were relatively rampant at that time, that Short Money could become a double whammy for his own party two generations later.

For when Labour fell into opposition at Westminster they always had the cash safety net of Short Money for their massed MPs North of the Border. Now their loss is set to be the SNP's gain if the polls are correct, with Labour's catastrophic deficit in membership relative to the SNP about to become a public funding one from which they may struggle to recover.

It all adds to a sense of structural change, with Labour yesterday saying farewell to the likes of Gordon Brown and Alistair Darling, the Liberal Democrats to stalwarts such as Menzies Campbell and Malcolm Bruce. All of them may well be succeeded by SNP members and the nationalists will gain both funding and formal influence at Westminster as a result.

Some of Ms Sturgeon's traditionalists may fear that extra influence and involvement at Westminster as a retrogade, corrupting step, but for now, with Westminster showing signs of panic, it's a problem they would rather have.