What should it take to win a border poll?

In the event of a border poll, what should victory look like?

Should a united Ireland be achieved by a slim margin or does there need to be some kind of weighted majority?

The former SDLP deputy leader Seamus Mallon believes that a simple 50% plus one majority in a border referendum would not "give us the kind of agreed and peaceful Ireland we seek".

He believes there should be "parallel consent", involving a majority of both unionist and nationalist voters.

Mr Mallon, who served as deputy first minister of Northern Ireland from 1998 to 2001, told the BBC's The View programme that without this change, there would be "chaos".

"Unfortunately, in the pursuit of unity, it would cause further and deeper disunity because it simply makes another minority a new minority," he said.

"You have a border poll, 50% plus one. Is that a victory?

"Is it a result that can sustain the tensions that will be in this island?

"How long would peace last in those circumstances?" he added.

Earlier this year, a group called Ireland's Future met at Belfast's Waterfront Hall to promote a poll for Irish reunification.

Belfast-based barrister Ánna McHugh, who spoke at the event in 2018, said Mr Mallon's analysis is wrong.

"If 50 plus one is good enough to retain the union, then it ought to be good enough in terms of a border poll," she said.

"I have to say, Seamus Mallon has himself acknowledged that John Hume did not give two balls of roasted snow about his advice, and I think that is where people are at with Seamus Mallon's advice this week."

However, the SDLP's current leader, Colum Eastwood, has defended his former party stalwart.

"I think it is a real disgrace the abuse Seamus Mallon has got over the past couple of days from political pygmies trying to attack a political giant who gave an enormous amount to this country and to peace," said the Foyle MLA.

"Some of the people attacking him could not lace his boots.

"I disagree with him on the mechanism.

"I think the mechanism that exists within the Good Friday Agreement is the right one."

But how would unionists respond to the prospect of a border poll?

Last year, the former First Minister Peter Robinson addressed this issue and echoed Mr Mallon's warning of "chaos".

However, Jeanette Warke, a community worker in Londonderry's Fountain estate, said Mr Mallon has struck a chord.

"I agree with Seamus Mallon," she explained. "He was often referred to as the wise old man from Irish nationalism, and it is very true.

"That man is wise. I would agree with him 100%."