The SDLP’s Nichola Mallon, Colum Eastwood and Brian Tierney celebrate the party's emphatic win in Foyle

Prominent amongst the theories floated to explain the unexpectedly crushing nature of SDLP leader Colum Eastwood’s victory over Sinn Fein incumbent Elisha McCallion is the idea that the people of Londonderry felt that they were without a voice.

Mr Eastwood’s decision to stand in his hometown constituency was viewed as a potentially risky move, just two years after his party lost the seat to Sinn Fein for the first time since it was created in the early 1980s.

But his decision was vindicated with the highest margin of victory ever recorded in Foyle, as the Sinn Fein vote collapsed.

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Sinn Fein’s Elisha McCallion, the DUP’s Gary Middleton, Aontu’s Anne McCloskey and the SDLP’s Colum Eastwood as the Foyle result was announcced

Former SDLP leader and former Foyle MP Mark Durkan is amongst those who puts the extraordinary election result down to disaffection with the lack of representation – both at Stormont and Westminster.

“People have kind of got past the kind of attitude of ‘a plague on all the parties’ houses’ that came through at previous elections and there was more discernment,” he said.

“People had a sense that they could vote to get a change both in terms of representation at Westminster and to send a message about wanting the Assembly and the north-south institutions back.”

Mr Durkan added: “People were making the point that Lady Sylvia Hermon’s interventions inside the Commons spoke for them, whereas Elisha McCallion’s interviews outside the Commons didn’t.

“People don’t want to be voiceless.”

The veteran socialist campaigner and former People Before Profit MLA Eamonn McCann expressed a similar view.

“I think the health service was a key thing but I think that by the end every party was claiming to be the party of the NHS,” he said.

“I think that abstentionism was a bigger factor. There has been a concentration, an understandable concentration, on voting in Westminster when things have been on a sort of knife-edge. There was a potential for parties from the North to have an effect on the outcome in any knife-edge vote. It had been widely commented on that by Sinn Fein not being there it made it slightly – not much but slightly – easier for Boris Johnson to win.”

Terry Wright, a former vice-chairman of the UUP and former chairman of its Foyle association who left the party in 2013, said he had a similar impression of the general mood in Londonderry.

“Colum’s key messages were about representation and getting back to work,” Mr Wright said.

“People were annoyed about Sinn Fein not taking seats because they felt that it could have made a difference on some of the issues that were being voted on, particularly in some of those very close votes.

“People are fed up with the lack of representation but particularly at Stormont, although the two are linked.

“There are a lot of people, in my generation at least, with grandchildren at schools and they are noticing the increased stress on schools.”

He added: “People are disgusted that the MLAs are still picking up money and doing nothing for it. They are worried about the health service and they want politicians to do something about it.”

Mr Wright believes Sinn Fein’s abstentionist policy might have won votes for the SDLP from more traditionally unionist voters.

“On the pro-Union side, there’s a lot of disillusionment with the DUP,” he said. “And they didn’t see a chance of taking the seat in Derry anyway, so people will have decided to vote tactically because they prefer someone who is going to take their seat.”

Manufacturing NI chief Stephen Kelly, who is from Londonderry, said: “We need as many voices as possible speaking up for us. In fairness to Sinn Fein, they used their influence very well on the EU side but in any negotiation it takes two sides.