Elmgrove tends to vote similarly to East Belfast as a whole, so it is a weather vane for the constituency.
That day back in May 2010 I got findings that had Mr Robinson only fractionally ahead of Mrs Long, by 53 to 52. The then DUP leader had been 12,000 votes ahead of her in the 2005 general election so I feared my Elmgrove exit polling data was a rogue result. I put it online quietly, smothered with caveats about it only being a small snapshot of East Belfast.
In fact it was the first hint that Mrs Long had done so well, and in fact it slightly underplayed her overall result in East Belfast. She narrowly unseated Northern Ireland’s first minister from his House of Commons perch.
Ever since I have carried out an exit poll at Elmgrove, and ever since it has given readers of this newspaper an early clue as to how East Belfast has voted, which in turn often gives us a first understanding of how Northern Ireland has voted.
On Thursday I stood out Elmgrove all afternoon and early evening. Out of 548 emerging voters whom I approached, 327 divulged how they had given their first preference vote.
When I tallied it all up for publication on the News Letter website at 10pm, the results were:
DUP 91 first preferences; Alliance 90; TUV 47; UUP 33; Green 23; PUP 22; Others 21
It was clear that while Alliance had again got out a big vote, the DUP vote had not collapsed as some polls had suggested.
But the most striking thing of all was the TUV vote. Their vote share in Elmgrove on 2007 had more than trebled (from about 4% to about 14%), as in the event it trebled across Northern Ireland.
I had noticed something during the day that had never happened in previous polls at Elmgrove.
Many DUP voters who emerged from the station told me that they had voted DUP, then TUV.
But I had not asked which candidate people had transferred to — I was processing hundreds of voters, which leaves time for only a few seconds per person, so I only asked the party to which they had given en their first preference and the party they had voted for in the last election.
Yet a large number of DUP voters wanted to volunteer the information that they had given the TUV a high priority. Some of these voters were saying that they were only voting DUP to stop a Sinn Fein first minister.
This reflects a hardening of unionist thinking and it helps to illustrate the massive challenge facing unionism.
Because there is a flip side of that determination to stop a republican getting the top job (symbolically the top job, even if it actually has the same powers as first minister).
The flip side is the liberal unionist view that the campaign to stop Sinn Fein becoming first minister merely drove nationalists to vote for the party.
There is evidence that exactly that has happened, with the small but noticeable swing this week from the SDLP to SF, with the former getting its lowest ever vote share in a major election.
Lee Reynolds, ex DUP advisor, said on TV last night that he had opposed a campaign that focused on stopping SF and a border poll.
The divide now within unionism as to whether or not to adopt a liberal, mainstream or hardline unionist approach to the challenges facing unionism is more stark than ever.
The headline figures are that the liberal approach, UUP, got 11.2% of the vote, the mainstream DUP approach got 21.3%, and the harder TUV approach got 7.6%.
Thus the divide within unionism was roughly 50% of unionists went for DUP, 30% went UUP and 20% TUV.
But it is likely that the DUP would have lost more votes to Jim Allister’s party, if not for the determination to stop SF.
However, it is increasingly clear that a single unionist party or movement will only worsen this divide.
At least some of the Ulster Unionist vote would go to Alliance or some other centrist party, thus causing the overall unionist vote to drop below 40%.
A dramatic example of the perils of taking such an approach was shown in the 2019 for Westminster election in South Belfast, when the DUP ran a very traditional unionist campaign, sharing a stage at times with loyalists amid flags.
This attempt to rally unionists suffered a crushing defeat in South Belfast at the hands of the SDLP (greatly helped by Sinn Fein standing aside, as nationalists responded to unionist unity with their own display of unity, a variation of which has happened this week).
Unionism is far from defeated.
Not only is it still ahead of nationalism on votes there are still reasons to believe that support for the UK enjoys the backing of a comfortable majority of voters.
But navigating a political approach that enjoys broad unionist support is going to be tricky.
I continue to believe that unionism needs to find a way to be attractive, and firm.
It is often firm, but unattractive.
It is sometimes attractive, but also weak.
As this column often argues, all sorts of sometimes small things are happening to undermine NI’s place as a full part of the UK by attrition. That process will only accelerate under an emboldened Sinn Fein.
We badly need proper help from London. There are signs that this government understands that constantly tiptoeing around the grievances of separatists in Scotland and NI does not work.
We need this awareness to be turned into more active help for unionists.
• Henry McDonald: Sinn Fein’s day in the sun but no new dawn for Irish unity
• Brian John Spencer: Unionism was given no wriggle room by nationalism