Winning 45% of the vote in the independence referendum was a huge achievement for the Yes side, but even for confirmed Yes supporters there is no doubt why the campaign to take Scotland out of the UK fell short.

The economic prospectus on which the SNP Government’s case was built left too many questions unanswered and many Scots were worried about the country becoming worse off.

The SNP, despite wanting to sever political ties with the UK, backed a macro-economic partnership in the form of a currency union.

The proposal, in theory, was simple: sterling would be shared and the Bank of England would be the lender of last resort for Scottish financial institutions.

In practice, a currency union required the consent of the rest of the UK but in the end the door was slammed in the face of Scotland by George Osborne - then Tory Chancellor of the Exchequer.

Alex Salmond and the rest of the Yes campaign had to spend the entirety of the referendum promoting a constitutional option without being able to guarantee the currency that would rest in people’s pockets.

As we report today, however, SNP MPs are now conducting a review of the alternatives to currency union.

A separate Scottish currency – either backed up by a new central bank or a currency board – is an option with growing support amongst the party's elected representatives.

A separate currency was always an option that carried opportunities and risks, but it looks to be a much more attractive proposition this time around.

Last month’s Brexit vote, which led to Sturgeon saying a second independence referendum is “highly likely”, changes everything.

If the UK pulls out of the EU against Scotland's will, and if this nation then subsequently votes to leave the UK, it would make little sense to share a currency with a country that was outside a union Scotland was staying in.

The default positions of UK politics just now are either chaos - the turmoil of Brexit; a hopeless Labour party with no prospect of becoming a government - or anathema to the over-riding view of most Scots: a right-wing Tory Government that can look forward to enjoying power for at least another decade.

Basing independence on a new currency certainly carries a risk, but so does staying in a union that brings little chance of progressive change.

What is certain - for all of us who want to see an independent Scotland - is that beginning the big discussion now on such a vital and contentious issue as currency is the right thing to do. This time around the hard work must be done early.