Isabel Oakeshott is co-author with Lord Ashcroft of Call Me Dave.

It may be the season of goodwill, but the prospect of the two rival Brexit campaigns kissing under the mistletoe now looks less likely than a white Christmas.

Tentative talks between Vote Leave and Leave.eu have collapsed amid continuing mistrust between the key players. It means they will compete with each other all the way to the finishing line next year, when the Electoral Commission will be forced to designate one or the other as the official campaign.

Representatives from Leave.eu and Vote Leave recently met to discuss how they might be able to work together. It followed a formal overture from Arron Banks, the multimillionaire businessman behind Leave.eu. Writing to Matthew Elliott, chief executive of Vote Leave, last month, Banks had declared that he had “no prior conditions” for a merger. Following this gesture, the Board of Vote Leave felt it would be churlish not to hear him out.

Present at the confidential talks, held at a neutral location, were Banks himself, Leave.eu co-chairman Richard Tice, Vote Leave’s Treasurer John Mills, and Vote Leave’s director Daniel Hodson.

During what is described as a “cordial” meeting, Mills and Hodson were frank about their reservations. They cited what they see as Banks’ “erratic” behaviour and his determination to put immigration at the heart of the Brexit campaign as key barriers to a full merger. They also raised the thorny question of the role to be played by Nigel Farage, over which the rival campaigns disagree. (Vote Leave believes Farage is too divisive and politically damaged to lead the campaign, whereas leave.eu believes he must be at the forefront.)

Despite the sensitive personal nature of some of these questions, insiders say there was a positive atmosphere. It is understood that Banks acknowledged that Elliott has better Westminster connections and is a more effective political operator than himself. (His own political experience is limited to his dealings with UKIP, to which he donated £1 million in 2014.) The businessman indicated that he was ready to let Elliott, who founded the TaxPayers’ Alliance and (along with another of Vote Leave’s treasurers, City financier and philanthropist Peter Cruddas) ran the successful No To AV campaign during the Coalition, front the political campaign.

A source close to Banks said: “Arron knows that Matthew is better at political schmoozing. He suggested that Matthew do the geeky political stuff, and we focus on the mass marketing; the ground campaign. “

While the Vote Leave camp continued to play down the prospect of a formal merger, various ways in which the two campaigns could co-operate were discussed. It ended amicably, with a further meeting mooted.

To the surprise and dismay of Vote Leave however, the day after the crunch talks, Banks emailed Elliott declaring that he did not wish to hold any further discussions. The missive brought the flirtation to an abrupt end.

What happened? Quite simply, personalities. Banks has a problem working with various figures in Vote Leave, the latest of which is Campaign Director, Dominic Cummings. He considers Cummings counterproductive to the cause.

It is true that Michael Gove’s former special adviser is divisive – so much so that when the Tories entered government in 2010, David Cameron’s then director of communications Andy Coulson vetoed his appointment as a special adviser. In a vicious character assassination CLICK HERE last month, the lefty polemicist Nick Cohen labelled him “the most self-aggrandising and destructive agitator the modern Tory party has produced” and suggested that he could “wreck” the campaign to persuade British voters to back leaving the EU. Having once been at the sharp end of Cohen’s poisonous pen myself, I know his harrumphing should be kept in perspective, but he is right that Cummings’ uncompromising style can alienate sensitive types.

The irony is that Cummings is nowhere near as divisive as Banks himself. The diplomatic Elliott has done his best, but a number of donors – and potential donors – have apparently told him in no uncertain terms that they want nothing to do with the Bristol-based businessman.

Banks knows all this and claims he is willing to take “half a step back” in the interests of a merger. However, he is not prepared to “leave the room completely.” And half a step is not enough for Vote Leave.

Thus it is stalemate.

During last week’s talks, Tice suggested that if the two campaigns came together, a new Board could be established to oversee the running of the joint operation – or rather, to keep the peace. If this sensible move had been suggested six months ago, perhaps it would have worked. It is now too late.

While Elliott remains quietly confident his campaign will secure the official designation, Banks shows no sign of walking away. The energetic businessman believes his good name has been “blackened” as a result of the long running tussle, and wants to set people straight. In the New Year he will embark on a charm offensive to persuade people that he has been misrepresented. He believes it won’t take much to win over his critics.

A friend says: “Arron is finding that people who have heard a lot about him but never actually met him are pleasantly surprised to find he doesn’t have three heads. He believes that all the briefing against him is actually quite helpful in that respect.”

For his part, Elliott is keeping his head down. To borrow a phrase favoured by government ministers when they are under pressure, he is “just getting on with the job.” In the war of attrition, he has yet to play all his cards.

For all those who want the “out” campaign to morph into the mighty machine that will be required to persuade an intrinsically cautious electorate to back Brexit, the failure of the two camps to come together is a big disappointment. Unless there is a last minute détente, either Banks or Elliott is going to be badly burned. When the story of the referendum is written, any evidence that the outcome was adversely affected by their failure to work together will mean history is less kind to both men.