When we saw the data, frankly we struggled to believe what it was telling us. Totting up the totals up to Wednesday night, Vote Leave had 620.9k followers across Twitter, Instagram and Facebook, compared to Remain's 595.8k.
Historically social media, has not been a clear predictor of electoral success. But on voting day, the markets were up, and the most recent polls had indicated Remain was going to win.
Ironically for a socially-led agency, we were not sure if we could trust the channel trends. After all, 46,500,001 people turned out to vote, making social media support a drop in the ocean. But it was telling us something: Leave was going strong.
Clearly, there are some lessons to be learned for any future political campaigns.
1. Short term campaigning is vital - but get your messaging clear early on
YouGov has hypothesised that most people - especially those not normally interested in politics - start paying attention not when campaigning begins, but in the immediate run-up to polling day. On both sides of the debate, interest rocketed in the run-up to the poll, but it was the month before, rather than the last week, which made the most impact.
Both sides enjoyed a rise in fans or followers in the last 30 days, with Vote Leave's growing the most, with an increase of 134.5k fans compared to Remain's 121.7k. Leave also had higher engagement scores across all three platforms. Its followers were particularly active: liking, commenting and sharing in larger numbers than those on the Remain side. For many, this was the referendum they had long been waiting for.
In the last week, Remain suddenly began to attract around 13-15k followers a day, compared to 10-12k for Leave. But arguably, it was too late.
2. Big names help...
Remain managed to widen its appeal in the final countdown by capitalising on celebrity endorsements. Most people were by that stage aware of the politicians with most cut-through on social: David Cameron and Sir John Major for Remain; Boris Johnson and Michael Gove for Leave. But things improved for Remain through Daniel Craig's Instagram support - its single most engaged with post - and a much-liked Facebook video of Sheila Hancock's heartfelt speech about tolerance and inclusion on the eve of polling day.
By contrast, Leave missed a trick by leaving its non-political big names, including Sir Michael Caine, Sir Ian Botham and Dame Joan Collins, out of its campaigning in the final days.
3. ...But not as much as involving your supporters...
Boris Johnson and Michael Gove may not seem natural Instagrammers, but the Leave campaign was particularly strong on the platform, with almost double the followers than Remain. Their success arguably reflects Leave's wider strategy - to position themselves as being on the side of a the UK's sizeable disenfranchised majority.
Not only did Leave post five times as much as Remain, but the crucial difference was the content they used: a host of photos starring grass-roots campaigners. By understanding the way people use Instagram and engage with followers, Leave was able to garner genuine support and crucially, give a voice to their campaigners.
Leave also had the edge on Twitter, with 20k more followers than Remain. While both sides used Twitter to share commentary on live debates and retweet high profile figures, Leave's most popular posts again involved their supporters, asking them to retweet to show they are voting, whereas Remain's most popular post was about David Beckham's support for the campaign.
4. Think visual
Remain's last minute posts of high profile celebrities (e.g. Daniel Craig and Spencer Matthews) were big hits, but they did not really leverage the potential of Instagram, despite the size of the platform (an estimated 14m UK users).
Looking further back, Remain's posts focussed on the potential cost of Brexit; text-based posts which gained much less engagement. Campaigners take note: Instagrammers will be far more engaged with visually appealing or fun content, not rhetoric.
On Facebook, both sides prioritised videos and visuals in the last 30 days, perhaps realising they were key to shareability and engagement. Non-visual updates dropped off almost completely, and support was driven by poster-style graphic updates and videos of the key figures making the debate.
So what have we learnt
Social media is not just there for broadcasting your views. It's a crucial tool for engaging potential voters, giving them the feeling that they have a voice, and making them feel part of a larger debate. Future politicians should pay attention to the way both campaigns talked to voters in social, and understand how each channel was used to drive meaningful engagement.
Social media campaigning was already front and centre in the General Election of 2015, and the EU referendum has brought it into the fray to an even greater extent. Whatever happens in the fallout of this stratospheric change in Britain's history, socially savvy campaigning is here to stay.
We Are Social analysed the Leave and Remain official campaigns across Facebook, Twitter and Instagram, for four weeks up to and including Wednesday, June 22nd.