In a candid chat about his childhood, the Gardeners' World star, 68, revealed that he was a "troubled" teenager and described himself as a "black sheep in the family" – a concept that is hard to marry with his sunny disposition on TV.
He told The Guardian he was "very privileged" and went to boarding school from the age of seven. Despite being expelled, he did not struggle academically and went on to study at University where his life took a drastic turn thanks to his future wife.
"Two things happened. First, by being the black sheep in my family, I always felt able to escape it," he began.
"Second, I was lucky enough – it’s really basic – to meet somebody that I completely fell in love with when I was young and we became the team.
"I went from a life that was complicated and difficult, and I was troubled. I was a difficult person. In a different environment, I definitely would have ended up in prison," Monty continued.
After dating for several years, the couple got married on July 29 1983. Although Monty has kept his wedding day largely private, he made an exception on their 39th anniversary to share a rare throwback photo.
Standing outside a set of wrought iron gates, Monty's bride Sarah looked stunning in an unconventional cornflower jacket with large buttons down the front, which she paired with a chunky necklace and matching earrings.
Meanwhile, Monty rocked the same thick curly hair and big grin he is known for today, alongside a cream suit and black spotty tie.
"We got married 39 years ago today - the picture is a little faded, a little wrinkly, like us but the love is as evergreen and strong now as it was all those years ago," wrote Monty, who is now a proud parent to three children, Tom, Adam and Freya.
In the same chat with The Guardian, Monty revealed how his wife would react to him being called a sex symbol. "Well, I feel slightly embarrassed, sort of smirky. My wife would say: ‘Look at you smirking at that question.’
"I’ve been living with somebody for 43 years, who I love more and more, so on one level, it’s so irrelevant as to be silly. On another level, I’m human – I’d rather that said about me than not. But I can’t tell you how insular my life is outside work. I go in the garden. I see a few people every day, usually the same people. I like them very much and not one of them thinks I’m remotely sexy."