They're on the march - the leaders of Britain's three main parties are heading to Scotland together in a rare show of unity.

The Prime Minister will also miss his traditional parliamentary questions.

That's unusual and a sign perhaps of the growing concern over the referendum on Scottish independence.

BRITAIN'S PRIME MINISTER, DAVID CAMERON, SAYING:

"I want to do everything I can to put the arguments in front of the people. In the end it is for the Scottish people to decide but I want everyone to know that the rest of the United Kingdom and I speak as Prime Minister want them to stay."

Latest polls suggest the result is too close to call.

And new measures, including tax breaks, are being offered by the government to sway the undecided to No.

But the leader of the Yes campaign says the moves are a sign of panic.

ALEX SALMOND, SCOTLAND'S FIRST MINISTER AND LEADER OF THE YES CAMPAIGN, SAYING:

"I doubt if I have even seen a political campaign in any election, never mind a referendum, which has fallen apart at the seams in such spectacular fashion."

What currency Scotland will use in the event of a split from the UK is one big question.

The Bank of England says a currency union isn't compatible with sovereignty - and there are fears worried bank customers could vote with their wallets.

George Hay is from Reuters Breakingviews.

GEORGE HAY, REUTERS BREAKINGVIEWS, SAYING:

"People may worry that the value of the pounds that I have got in my Scottish bank is not the same value as if I had them in an English bank so I am going to take them out and put them in an English bank."

Scotland's been printing its own bank notes since 1695.

And 13% of all people employed in banking in the UK are in Scotland.

But BGC's Mike Ingram fears the 307-year-old union could be about to end.

MIKE INGRAM, MARKET COMMENTATOR, BGC PARTNERS, SAYING:

"By this time next week it could well be that we see Scotland as an independent country and I am going to have to be getting a passport just to travel to Edinburgh."

Financial markets were steady after sterling's pounding on Monday.

But the turmoil has increased the risks of another split too.

One report suggests the chances of Britain leaving the European Union in the event of a Scotland exit are now fifty fifty.

And as for Scotland's continued EU membership - that's not guaranteed either.