The loss of three SDLP seats, all of which were held by former party leaders, and most notably the loss of the former power base of John Hume in the Foyle constituency has brought the very existence of the party into question.

It marks the end of an era and a political earthquake that has been slowly evolving for almost two decades.

Yet when it came, it still sent shockwaves across the faces of commentators, politicians and political anoraks.

The SDLP was not alone in meltdown.

Northern Ireland results in detail

The Ulster Unionist Party, which had held two seats, was also buried in Westminster electoral terms overnight, losing both of its seats in South Antrim and Fermanagh & South Tyrone.

The two parties so central to the Good Friday Agreement will not be represented in Westminster 19 years after the signing of the historic deal.

The parties of Hume and Trimble are no longer on the Westminster electoral map.

Sinn Feín leader Gerry Adams said that a referendum on Irish unity is now inevitable after the dramatic shift among Northern Ireland voters.

As the middle-ground parties collapsed, Mr Adams said unionists had only secured less than half the electorate's backing for the first time in the region's history, while nationalism had clearly turned its back on Westminster.

Speaking in Belfast, where he also urged for power-sharing to be restored in Northern Ireland, Mr Adams said: "One thing we can say for certainty, there is going to be a referendum on Irish unity. I can't say when, but there is going to be."

Bono, Ulster Unionist leader David Trimble and SDLP leader John Hume in May 1998 

For the SDLP, the defeat of Alasdair McDonnell, Margaret Ritchie and Mark Durkan combined with the abstentionist policy adopted by Sinn Féin means there will be no nationalist representation in the UK parliament.

For Mr Durkan, the man who had carried the Hume mantle, the defeat was hard to take; his speech after the declaration marked out by an apology to John and Pat Hume.

In her acceptance speech, newly-elected MP Elisha McCallion simply said "we did it for you Martin", referencing the late Sinn Féin Deputy First Minister Martin McGuinness who died in March.

Elisha McCallion with Sinn Féin NI leader Michelle O'Neill

In South Belfast, Alasdair McDonnell lost to a resurgent DUP with Emma Little-Pengelly winning the seat.

Nigel Dodds,EmmaLittle-Pengelly and Gavin Robinson

In South Down, the electoral success of Sinn Féin in the March Assembly elections manifested itself yet again as Chris Hazzard saw off the challenge of Margaret Ritchie.

Mr Hazzard said his victory meant "the roadmap to Irish unity was appealing to all and in need of serious exploration".

Chris Hazzard

Current SDLP leader Colum Eastwood spoke of a "very, very difficult day for the party".

Describing his defeated colleagues as "three political giants who had made an immense contribution to political life", Mr Eastwood said his party would return to political talks on Monday next in a bid to restore the Stormont institutions.

He said he was an optimist but also a realist, and he simply hoped that Sinn Féin and the DUP could do a deal to restore power-sharing.

As the two winners of the night, the DUP and Sinn Féin prepare for those negotiations buoyed by their enhanced political mandates, while the SDLP and Ulster Unionists face deep and searching questions as to their very viability.