On a twisting turning circuit around Birmingham, which included a series of punishing climbs, six-time Paralympic champion Weir looked to be coasting to victory.
But an untimely puncture allowed Smith to catch him with just six miles remaining, upgrading the silver medal he won four years ago on the Gold Coast.
“I don’t want to win by default, but I think I deserve this gold, it’s what I’ve trained and worked for,” he said, after Scotland’s Sean Frame and England’s Simon Lawson completed the podium and Weir came seventh, 23 minutes behind the winner.
“That’s a special upgrade, from a silver to a gold. It’s a real moment and hard to take in. I’ve trained for 16 months solid for this, the last ten weeks have been a huge training block for me, I’ve never worked harder for anything in my life.
“I told my closest friends and family that I was going to win a gold and I did it.
“I’m not taking anything away from myself, but David dropped me at mile five, I was chasing him hard, but I don’t know what would have happened if he hadn’t got that flat, I think I’d have closed him down and it would have been a sprint finish.
“Do not write off David Weir, he’s 43 years old and he’s still a supreme athlete. He should be Sir David Weir as far as I’m concerned, he’s a machine.”
Born into a Traveller background and living in Kent, Smith was a keen amateur boxer and training to be a plumber and plasterer. However, his life changed aged 16 when he was shot in a case of mistaken identity by a farmer.
Smith’s sporting journey began with wheelchair body building and powerlifting but after watching Weir’s four golds at the London Paralympics in 2012, he switched to wheelchair racing.
And what started with an internet search – “Where does David Weir train?” – came full circle as he claimed this gold.
“When I first met Jenny Archer (Weir’s coach) she was pretty blunt, she told me to lose four stone – that was the moment this all started,” he added.
“I don’t care what you do or who you are. I’m from a working-class background, I’ve got no airs and graces. But I had a dream, set my goals high and stayed positive. I knew I could achieve the impossible and I’ve done it.”
Weir insists he wanted to retire after 2012 but didn’t because of the lack of British talent coming through the system. He is still going aged 43 and it’s a claim he can no longer make.
“It’s tough to take that, I was going really well. I had a gut feeling, I even thought about taking a spare on the race which I’ve never done but I didn’t want to jinx myself,” he said.
“It’s not happened since the London Marathon in 2010, the timing pretty much sucks. I should have left my training tyres on; I’ve been racing on them for weeks without any problems.”
Eden Rainbow-Cooper, who Weir enrolled as his academy as a 13-year-old, took silver in the women’s race in only her second marathon.
“I’ve known David Weir since I was a teenager, he’s made such a special contribution to my career. We’re so close, he’s never wavered in his belief in me,” she said.
“Everything is racing through my mind. I was just hoping for a personal best. I never in a million years thought I’d win a medal; I was just hoping to enjoy it.
“That course was insane, the gradient on those hills at the end, that really tested me to the limit.
“I know I need another ten marathons to really understand this discipline. I’ve got a long time to learn this but I’m so excited to get back to working.”
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