Martin Findlay and his wife were travelling back to Aberdeen when they decided to use their six-hour layover to go and pay their respects to the Queen.
Arriving at Buckingham Palace to join the “long snaking line” of people commemorating the monarch, the couple said there was a blend of sorrow and “genuine warmth and British comradery”.
Mr Findlay said when the new King arrived there was a “real outpouring of affection”.
He said: “I think this took some people by surprise because I think most people were there to pay their respects to Her Majesty the Queen who was almost universally respected and liked in the UK and around the world.
“We just happened to to be in the right place at the right time.
“We just expected to see the car swooping through the gates but he stopped and there was just this huge cheer.
“And then we realised he was actually walking and spent quite a decent amount of time shaking hands or getting his hand kissed by one person I saw on the news.
“People were being very respectful passing on their condolences and I think everybody was just in awe of the fact that they were there witnessing a new King. It was quite an amazing time.”
The Queen passed away in a part of the world she loved
Many well-wishers have also been laying flowers and tributes at Balmoral Castle where the Queen died on Thursday afternoon.
The 55-year-old said they were both in New York when they heard the news.
“We were very sad,” he said. “We were in New York at the time and you could tell that that country holds a huge amount of respect for the Queen as well so you could tell it wasn’t just a UK story, it was a global story.
“It kind of hits you in ways you wouldn’t expect. She’s somebody who has always been there and is no longer there, she’s somebody who has defined Britain over the last 70 years. It was sad but also very sudden.
“On the one way it was heartening that it appeared to be something that had happened quickly and quite peacefully and also importantly for us coming from Aberdeenshire and Aberdeen, that she passed away in part of the world that she loves and is peaceful.
“What better place to end her 96 years than in a castle that she loved.”
The new King will ‘plot his own course’
Having met King Charles III in Aberdeen years previously, the office senior partner at KPMG said the new King was not one to be underestimated.
Speaking to the monarch at the opening of a new facility at Sir Jim Milne’s Balmoral Limited, Mr Findlay said: “He’s clearly a very intelligent person who’s interested in things.
“He will not seek to be the same as his mother he will plot his own course his mother adapted and changed the monarchy to adapt modern circumstances and he will have to do more of the same to keep it relevant to the UK and the Commonwealth.
“I wouldn’t underestimate his ability to show appropriate leadership to make that happen.”