IT WAS another strange day on the campaign trail.

Westminster destroyed the convention of Purdah and came out campaigning, sending out an entirely new Unionist trope.

Holyrood's Labour, Conservative and Liberal Democrat leaders stood shoulder to shoulder to promise a "delivery plan." And David Cameron, Nick Clegg and Ed Miliband announced they were abandoning these conventions to head North at the same time.

The Lamont/Rennie/Davidson announcement always looked strange. Done at the beck and call of Gordon Brown it looked even more odd. Trumped by Cameron/Clegg/Mililband it just looked pathetic. How had this been formulated? In case anyone doesn't know it, after Purdah is declared ahead of a major election Governments are meant to make no new announcements.

On Sunday the Chancellor of the Exchequer made a new Westminster Government announcement, then handed the baton to Gordon Brown as if to legitimise the breach.

So there was a sub-text to yesterday's announcement by the three Opposition parties at Holyrood. Vague didn't begin to describe it, given that each of these parties has its own proposals and leaders arriving today. So no-one can say what will emerge at the other end of the process to be enacted by the next Westminster Government.

The trio gathered on the terrace of Dynamic Earth, the geology museum round the corner from the Parliament and thus convenient for the staffers, who formed a backdrop brandishing placards proclaiming, "The best of both worlds for Scotland."

Johann Lamont, Ruth Davidson and Willie Rennie each made brief opening statements best summarised by these placards. Then it was opened up to questions from television broadcasters and it began to turn ugly. "With barely a week to go the poll, is this plan evidence of incompetence or panic?" one asked. "I'm certainly not panicking," replied Ms Lamont in a shrill, slightly panicky tone.

After that it all broke up without the newspaper journalists being allowed to join in the fun. Instead we got a background briefing from a Better Together adviser who we are not allowed to name.

We had just seen three MSPs make promises about something that only Westminster can deliver. How does that work? Because Gordon Brown says so. What, a backbench Labour MP? David Cameron has agreed. So you, the No campaign adviser we are not allowed to name, are speaking with the authority of the Prime Minister. Yes.

Strange times.