He is wearing a pair of jeans and a blazer on loan from his father. The constituency, after all had been a safe Conservative seat until 1997, when the Liberal Democrats took it.
The then newly-chosen leader of the Tories, Theresa May, had called the snap election following former Prime Minister David Cameron’s resignation.
Despite a few early shocks up and down the country, there was still little feeling that Labour would take Hallam – hence the casual appearance of the party’s candidate.
Half-an-hour later, though, and he had reason to be grateful for the raid on his dad’s wardrobe – he had just been asked to start drafting a victory speech. Another 30 minutes later, he took to the podium and made it with Mr Cameron’s former deputy Nick Clegg looking on behind him.
“Quite frankly, I absolutely wan’t expecting it,” Mr O’Mara said after winning the seat.
Labour wasn’t expecting it either. The party was not expecting to improve on its share of the vote from 2015, when Oliver Coppard ran a well-publicised campaign but fell 2,353 votes short of taking.
Mr O’Mara became the third MP in parliament with cerebral palsy, having previously worked as a music events organiser and disability campaigner in the city.
He pledged to continue that campaigning in the Houses of Parliament.
But his downfall began within just two months of replacing Mr Clegg when he was stripped of the Labour whip because of comments made online before standing for parliament.
His whip was reinstated in July 2018 following an investigation only for him to resign from the party nine days later.
More recently, he closed his constituency office for a month in April, all his staff were either sacked or walked out with at least one tribunal pending and he stopped holding surgeries or responding to correspondence from the public for a period of time.
Then, just weeks ago he said he had got a fresh team behind him and was operating from a new office in the city centre.
Mr O’Mara, who has previously spoken of his disabilities and mental health difficulties, was then left to pick up the pieces after his former chief of staff resigned in the most spectacular fashion following a foul-mouthed rant on the MP’s own Twitter account on Tuesday.
Gareth Arnold posted on Twitter how Sheffield Hallam ‘deserved so much better than him’ and labelled him a ‘selfish, degenerate p****’.
And then the final straw for Mr O’Mara came when The Times published further details of the sexual harassment claims, including that he felt a female member of staff had ‘repressed sexual feelings’ for him and claimed he also told his staff: “I’ll have to nickname myself ‘Thrush’ because I irritate c***s.”
While much of Mr O’Mara’s two years representing the constituency has been characterised by controversy and criticism, this week may have been the most challenging yet for the 37-year-old.
The Times published WhatsApp messages it had seen, in which Mr O’Mara described the sexual attraction he felt for the member of staff.
When asked to comment specifically on the allegations, Mr O’Mara said: “It’s all true.”
That comment was one of the most alarming aspects of this entire saga and confirmed months of speculation about Mr O’Mara’s conduct.
It also confirmed worrying reports about the MP’s health, as it went on to say: “Now please respect my privacy and allow me to focus on my health rather than trying to drive me to suicide again with straw man sensationalism about my views on sex and equality.”
Given the events earlier in the week, the actual author of the statement could not be confirmed but it contained alarming language about the health of an MP – a man elected to represent the views of more than 70,000 people, 70,000 people who pay his £79,468 salary.
He has spoken previously about his mental health and attempts to take his own life – yet, still no help was forthcoming from the leaders in Westminster
While other MPs did offer assistance, what this whole saga has exposed is a sheer lack of support for politicians so that they are then able to help their constituents.
Among the many, lengthy statements and quotes of this week, one which really hits home is one by Mr O’Mara chief of staff Gareth Arnold.
Mr Arnold, who describes himself as a blogger and a digital marketing professional, rose to prominence in 2014 when he set up a social media account called Britain Furst, which was intended to troll the right-wing political group Britain First.
But, whatever people’s views of Mr Arnold – of which there have been many voiced since we spoke exclusively to him on Tuesday – one quote he gave during that interview, sums up where the main issue in this whole saga is.
He said: “The problem is that the recall procedure isn’t unfit for purpose but it’s purpose relies on the fact that MPs have a moral conscience and if you want to be on £78,000 a year and sit in your house and do nothing there's nothing to stop you at all.”
The Recall of MPs Act 2015 states that the petition officer will open a recall petition if an MP has been convicted of an offence and received a custodial sentence or ordered to be detained, been barred from the House of Commons for 10 sitting days or 14 calendar days or convicted of providing false or misleading expense claims.
One thing that surely everyone can agree on is that Mr O’Mara’s turbulent two years have shown is that constituents are left helpless until their MP does any of the above.
Fortunately for all involved that didn't happen in this case but it has certainly exposed serious flaws in policies at Westminster.