Who will lead the Unionist campaign for Labour in Scotland this time around?

Barely three years ago an alliance of senior Labour figures helped see off an intense campaign for Scottish independence.

Alistair Darling, the ex-chancellor, led the cross-party effort for a No vote and was helped by a series of barnstorming interventions by former colleague Gordon Brown and the passionate Scotland-wide tour carried out by former secretary of state Jim Murphy.

Now, however, there appears uncertainty as to who could lead a unionist campaign while the backdrop to the vote – Brexit, a relatively new prime minister and a Corbyn-led Labour Party – is very different.

There are likely to be occasional interventions from both Jeremy Corbyn and Sadiq Khan but two London-based politicians cannot play a substantial role in the vote. The Labour leader had hoped his anti-austerity message would help the party boost its poll ratings in Scotland but that has yet to happen. Khan, the London mayor, is well-liked across the party and has the largest personal mandate of any politician in the country but his comments last month, when he suggested nationalism could be as divisive as racism, caused immense controversy.

So which Labour figures could lead the case for Scotland to remain part of the Union?

Gordon Brown – the former prime minister who last week confirmed he had begun work on writing his memoirs.

Lord Darling – the chairman of Better Together in 2014 won praise for his relentless efforts and calm approach.

Kezia Dugdale – the leader of Scottish Labour is well-regarded by party colleagues but it has long been thought that another No campaign would be led by someone outside of the daily to- and fro- of Holyrood politics.

Jim Murphy – the former cabinet minister is a seasoned operator and proved a teak-tough campaigner last time around – in the face of nationalist abuse – but the Blairite ex-MP may be cautious about teaming up with Jeremy Corbyn.

JK Rowling – the multi-millionaire author and Labour donor “has come up several times in conversations among unionist politicians”, The Times reported today.

Yesterday a BMG poll for The Herald put support for independence at 48 per cent, and for the unionist case at 52 per cent, once “don’t knows” had been excluded.