A leading Scottish business figure
A senior Scottish businessman is being considered as the leader of the campaign to save the Union in a bid to highlight the economic risk of independence.
Keith Cochrane, the former chief executive of engineering giant The Weir Group, and Sir Ian Wood, the North Sea oil tycoon, are both among possible candidates for the role.
It comes amid a growing consensus that a non-political figure will be best-placed to take on the SNP and bring together the unionist campaign.
Mr Cochrane, who last year stepped down from his role at The Weir group, said recently that Brexit only increases the importance of the Union.
"Anything that has the potential to create greater uncertainty is unhelpful," he said. Sir
Ian Wood played a pivotal role in the 2014 campaign when he warned that the SNP's predictions for the recovery of North Sea oil were too high.
Lord Darling of Roulanish
Lord Darling, the former Labour Chancellor, ran the successful Better Together campaign in 2014 and directly took on the SNP during head-to-head debates.
He is unlikely to reprise the role but has already shown that he is prepared to join the fight. He told BBC Radio 4's Today programme earlier this week: “If Nicola Sturgeon’s argument is OK, the UK voted to Leave but Scotland is different. What’s the deal between Scotland and Europe? We simply don’t know.
“I think it’s highly unlikely that Spain for example, would allow a situation that Nicola Sturgeon wants, that somehow the UK can leave but Scotland can have its own carve-out.”
Gordon Brown, the former Labour Prime Minister, was also credited with one of the most significant interventions of the referendum after a passionate speech in the final days of the campaign.
However Labour has made clear that the party will not campaign alongside anyone else during the independence referendum in the wake of the party's decimation in Scotland during the General Election.
Mr Brown said in his referendum speech: "Scotland does not belong to the SNP. Scotland does not belong to the Yes campaign. Scotland does not belong to any politician. Scotland belongs to all of us.
“What we have built together by sacrificing and sharing, let no narrow nationalism split asunder."
Theresa May or Ruth Davidson
The Prime Minister will play a central role in any referendum campaign but will not lead it.
There are significant concerns that appointing a Conservative politician to lead the over-arching unionist campaign will play into the hands of the SNP.
Ruth Davidson, the leader of the Scottish Conservatives, will head the Conservatives campaign in Scotland but as a Tory politician it would be almost impossible for her to lead a cross-party campaign.
She is hugely rated by the Conservatives and has already been taking the fight to Nicola Sturgeon, the SNP leader, accusing her of going "full Donald Trump" over a series of tweets.
JK Rowling, the author, is considered as a potential leader for the campaign given her widespread appeal and passionate support of the Union.
She is seen as a non-partisan figure and is an outspoken critic of Jeremy Corbyn, the Labour leader.
In the last independence referendum campaign she directly took on nationalists who abused her on Twitter and refused to be deterred from defending the Union.
However it is thought she is unlikely to lead any campaign but instead make a series of high-profile interventions.