Self-described “aviation nut” Alan Meloy was on his front doorstep taking pictures of aircraft over the Sheffield suburb of Chapeltown when he spotted something a bit different flying up above.
He quickly photographed the unusual plane and immediately recognised it to be one of the two aircraft used as Air Force One, the name given to the plane which the US President uses.
At this point Mr Trump’s Iraq visit was still top secret - he and First Lady Melania had left Washington DC without fanfare in the middle of the night.
So when Mr Meloy posted the image on photo-sharing site Flickr to see if anyone else had spotted it, he was met with some scepticism - the plane was flying under a false callsign to keep the trip a secret.
But when other enthusiasts spotted the image and also recognised it as one of the two VC-25 planes used as Air Force One, they cross-referenced it with tracking data and deduced the president was likely to be on his way to the Middle East.
With the news being so widely discussed online thanks to the photo, a ban on reporting the trip, agreed with the White House press corps, was lifted.
Mr Meloy, meanwhile, has found himself the centre of attention on both sides of the Atlantic.
“It’s one of those weird moments where you’re right place and right time,” he told the Guardian.
“Boxing Day dawns clear and bright, the next thing there’s an interesting airplane.”