They meet at a work party, which is the first sign that something's very wrong with their life (who meets through work?) and they're both attracted at the start but just can't get along- they are fire and ice, oil and water, politics and mathematics, they are two spirits who couldn't be more different but gravitate towards one another anyway.
They end up in a dark room (Thomas' office) and David can't think of a worse idea than this.
It's all an accident, nothing done on purpose, and when it's finished, they don't say a word.
Both of them put their clothes back on, refuse to look each other in the eye, and when they emerge everyone assumes they were fighting. It's just how they are, nothing
They don't even remotely like one another.
David takes Constance out on a date (it's all fancy clothes and scented candles and the food costs more than the rent) and he realises that this is the worst way that he can think of to spend the rest of his life.
She nags all evening and he daydreams, thinking of a man who doesn't care about his job, his life, who doesn't care about him and it's all so much better that way.
Constance doesn't notice when he starts to take her lunch at work, flowers, chocolates- she loves the attention, revels in it and nags him all the more about ambition.
When he's lucky, he catches a glimpse of piercing blue eyes and sharp words and can't help but feel that strictly attraction is moving further away from the cards.
There's a Christmas party, and it's at a local pub.
In his defence, they are all very drunk.
Constance doesn't notice that he wasn't with her the entire night long, and David only knows that he spent the night with Thomas because they woke up next to each other, arms casually draped over one another and he couldn't escape fast enough.
Now that he's here, he wishes that he was back there. When he was there, he wishes he was here.
David's life is a complicated thing, and it's not getting any simpler, no matter how hard he wishes.
He finds Thomas' number in his phone.
He doesn't text.
Every time they meet, it gets easier and easier to insult one another over work and clothing and family and relationships and looks- everything's fair game.
Except, the one thing that they can never bring themselves to admit is that every little thing they criticise about is something they admire and are jealous of; David wants Thomas' ambition, his drive, and Thomas wants David's ability to exist contently on the sidelines and yet neither would swap it if they could.
All they are to each other is temporary relive from life.
Constance starts taking longer trips away. David knows she's dissatisfied with him and the life that he's built for her, but damn them all. He's happy and doing his best to compromise for her, but these things aren't in his nature.
He tries hard, he really does, but she's gone for days, weeks on end and he starts to find himself living in Thomas' flat, still unable to have a civil conversation and arguing over things from coffee to Pluto (David doesn't care what Thomas thinks. Pluto is a planet) but the mornings are worth getting up for again.
They go out once or twice in the evenings, but it's not the right sort of places for them.
It always ends up with takeaways, two different ones sat side by side on the insanely comfortable sofa.
David sends and receives his first text from Thomas.
It reads simply: a list of insults.
They understand the language well.
Constance gets home, David can't be bothered with drama so he bags a bag and goes back to Thomas.
She's fuming, he's upset, and they were like bread and butter, but now the butter has decided to coexist with marmite and the bread no longer has a place in the equation.
He returns home a week later and she's gone away; he invites Thomas over and they have sandwiches at David's house for once.
They discuss his marriage, and it's sad that the only thing that they don't argue over is the thing in David's life that causes the most argument.
There's make up around the sink when David drops by. Thomas isn't in (he's got his own key now) so he cycles in to the office and marches in, shoving the evidence in his partner's voice and demanding answers.
He's cheated on David, he knows it, so he punches Thomas in the face and walks out again.
They're no longer dating. Just like that.
Outside, he walks straight into Constance who of course heard only the parts about Thomas having an affair (she assumes that the world revolves around her) and suddenly that's gone too.
That's it, they don't meet up for years (3 years, 2 months and 11 days, but who's counting?) and Thomas marries a woman called Marilyn, who has a two year old girl and they raise her together.
David doesn't keep track of the news anymore. He doesn't want to see Thomas' face ever again, but then the whole alien thing happens and he has to.
The only thing to be thankful of is the fact that he manages to save Thomas' life.
After it's all over, everyone thinks that he'll get back together with Constance (the perfect ending, the perfect couple) and she pretends as though she's happy to, but he's not.
He gives it a month to check whether this is really what he wants or not, and it's not.
They break up after the three weeks, and David goes straight over to Thomas' house to apologise and ask out, then ends up staying there for a week and looking after Patricia, who really is very cute indeed.
He's got work to get back to though, so he leaves the two and stays over there for a few days, before deciding that he can commute from the White House.
Thomas proposes in public, in a McDonalds and David immediately agrees, kissing him right there even though he doesn't like public spectacles and people keep taking pictures of the president and his new fiancé.
They make the news the following morning and come out national TV, and Constance is finally happy with David and congratulates him for doing something with his life.
There's a lot of fire from the press, but neither of them care. It's their life.
The wedding is on a Thursday and David turns up in jeans and an old t shirt and Thomas forces him to put on a suit. They end up walking down the aisle together (by this point nobody cares about tradition) and everybody cheers and catcalls.
Steve wishes them a happy life together, and Dylan walks up to Patricia seriously and asks her for a dance.
They all laugh, and then proceed to dance but David can't stop falling over so they go sit on the side and drink unhealthy amounts of alcohol, laughing as the fat lady sings.
He can't think of a better way to spend the rest of his life.