Mr Obama's visit was accompanied by an article he authored, published in the Telegraph, addressing readers in the following way:
"As your friend, let me say that the EU makes Britain even greater".
Then Boris put pen to paper.
Boris Johnson used a column in the Sun newspaper, to try and claim that Mr Obama had shown proven anti-British sentiments since his first day as POTUS, by removing a bust of Winston Churchill from the Oval Office, and reportedly having it sent to the British Embassy in Washington.
His comments quickly attracted ridicule. Mr Churchill's own grandson, sitting MP Nicholas Soames poured criticism on Mr Johnson's comments, saying:
When the descendants of historical figures you've chosen to invoke start debunking your arguments, you know you're having a bad day.
Mr Johnson's comments largely drew criticism over him choosing to mention Mr Obama's part-Kenyan heritage, as part of his column. It echoes the sentiments that flared up in 2011, when Donald Trump demanded that Mr Obama release his birth certificate. Mr Obama found them, and as expected, they proved he was born in Hawaii afterall. He later roasted Mr Trump at the April 2011 Correspondents Dinner.
The fact that people keep bringing up the Kenyan connection is troubling; it comes down to an inability to provide a logical argument to whatever Mr Obama is championing. Instead of creating a rational opposing argument, Mr Johnson and Mr Trump have resorted to making ancestry the issue.
Some might simply call this an example of dog-whistle politics. It's been seen to an extent with the 2016 London Mayoral Campaign. Sadiq Khan was accused by rival Zac Goldsmith of "giving cover to extremists".
You could say this outburst by Mr Johnson is some kind of bonkers siren call to Britain's closet xenophobes. Maybe Mr Johnson is testing the waters, to see just how far he's allowed to go. Or he might just genuinely think the Kenyan thing actually matters.
Such a move might have backfired on the Brexit campaign however. Mr Obama enjoyed very high approval ratings amongst a sample of Brits polled by the Pew Research Centre in 2015. 76% of UK respondents had a lot of confidence that Mr Obama was "doing the right thing regarding world affairs".
In comparison, his predecessor, George W Bush was only about half as well-received across the pond. Here in the UK during the Bush Junior years, about only half of respondents thought he was doing the right thing. How times have changed.
Having the mascot for the Brexit campaign openly bashing a US President that Brits actually quite like is just the latest controversy in a campaign that's still got another 7 weeks left to go.