'Thank you, that's all I can say, diolch' – witnessing Geraint Thomas's final bike race as a pro cyclist where it started, Cardiff

What do Will Smith, Fontaines D.C., and Geraint Thomas have in common?

The trio have all played Cardiff Castle this summer, with the latter ending his career just outside its walls on Sunday afternoon, at the end of stage six of the Tour of Britain Men. Smith and the Irish band might not have had their own beer labelled for their events, this can being Mic Drop.

The rain, torrential at the start of the day, even paused for a moment as the 39-year-old crossed the line for a final time after a 19-year career. Along with thousands of fans, it was almost as if the weather was paying homage to the former Tour de France champion, two-time Olympic gold medallist, and everything else. Read out on stage, his palmarès is almost comical, given its length and breadth. There's the Tour, the Olympics, the Tours de Suisse and Romandie, Critérium du Dauphiné, Paris-Nice, National Championships, Commonwealth Games, podiums at the Giro d'Italia and Tour, and of course E3 Harelbeke.

It is not an understatement to say that he is one of the greatest Welsh sportspeople of all time, one reflected in the thousands of fans that greeted him in Cardiff on Sunday, and the presence of Wales' First Minister, Eluned Morgan. It was not overblown, it was deserved.

Amid the squeal of the disc brakes, the roar of the home crowd, the endless requests for signatures and selfies, it all finished for the Ineos Grenadiers rider where it began, on the roads of Cardiff.

It was scripted to be like this of course, the Tour of Britain organised so the race would pass Thomas's parents' house, past the Maindy velodrome where he first raced a bike, outside the castle, that symbol of Wales.

It didn't matter that he finished four minutes behind the race winner, Olav Kooij, nor did the race really matter; it was all about him.

"Thank you, that's all I can say. Diolch," Thomas managed on stage, bringing the curtain down on his professional career.

He has never been the most verbose, but it was clear that the moment had cut through, had got to him. All week, all year, the Welshman has been followed by his looming retirement, but here it was, finally happening.

The Tour of Britain, Britain's biggest bike race as it is, doesn't always attract the large crowds it deserves, but here, in the centre of Cardiff, there were almost overwhelming numbers of fans, all here to say farewell to their favourite rider.

At the start in Newport on Sunday morning, supporters were queueing up in the pouring rain to get inside the team presentation, there were people crowding round an open window into Thomas's final press conference, itching to catch a few words; it means so much.

"We watched a little montage on the bus now, and I felt myself already starting to choke up a bit" he explained pre-stage. "Macs [his son] and Sara, my wife, met us on the way in, so they were there. It was nice, but it's just so surreal. I think, like most stages this week, I've kind of forgotten that I have to do a bike race because it's almost like a celebration before the start, and then you get going, you're like, oh jeez, I've actually got that racing to do now. It’s definitely gonna be emotional."

It was emotional, with endless tributes paid to him. Thomas broke down on S4C, the Welsh broadcaster, and seemed on the verge of tears on stage at the end, but held himself back. "I'm not going to say too much because I think I'm going to break down again," he said. "Next question."

Beicio Cymru had given out over 11,000 masks of his face. "I've seen so many things in my face is a bit freaky to be honest," Thomas said. "No, I appreciate it so much."

"I think I feel really lucky," Thomas said before that final ride. "I kind of feel like I've been lucky my whole career with how things have panned out. Being in my prime for the home Olympics, the years I've had and finishing here and deciding to stop this year and and then have this weekend. The fact that the Tour of Britain's in September and I can do it as my last race is, it's all kind of aligned, it's unbelievable, really. I never expected that at all.

"It's stuff of dreams. It’s also strange that it's finishing because it's been my life since I was a junior. You're always thinking of the next race. You're always working towards something. So not to have that tomorrow morning will be strange. It’s the right time, for sure. I definitely don't regret it but it doesn't take away that it's weird."

Next, it's likely he will continue working for Ineos Grenadiers: "I’ve got a lot of knowledge as a rider, and I feel I can help the boys a lot, but there’s a lot of other stuff behind the scenes. That’s on the cards. It’s not definitely happening yet, but I’d love to continue with the team."

However, there is also a sense of liberty, as well as a bit of trepidation over what's next.

"I feel like I’ve got a lot of freedom to try other things, a few different sports, like triathlon or padel, and skiing. That freedom feels nice," Thomas explained.

"I’ll definitely still ride, I still enjoy riding my bike, I just won’t be pressing lap and doing efforts and that stuff," he continued. "I’m just going to enjoy it without the pressure and the thought of losing weight in the back of my mind. It's going to be weird, because all the routine will be gone.

"I’ve never been to prison, I don’t know what it’s like, but I guess you kind of get used to the way of every day, a certain running order. I’m guessing it could be quite like that."

Now, the celebrations will continue into the rainy Cardiff night, a "few beers with the boys" promised. Thomas has ridden off, but his achievements remain. Diolch.