The whirlwind journey for the Team Sky rider, from track and Classics star to Grand Tour champion, came to its end in France's Basque Country. He placed third in the time trial and defended the yellow jersey.
"It's just a whirlwind. Obviously crossing the line there was massive emotion," Thomas said in Espelette. "Hearing the stories of what it's like back in Wales. I've stayed in the bubble so I've no idea. It's insane."
>>> Five talking points from stage 20 of the 2018 Tour de France
Thomas had talked of the bubble all season, staying in it through various training camps and while winning the Critérium du Dauphiné. Today, he emerged and enjoyed himself.
"It was emotional. I didn't know my wife was here either, which kind of made it worse. It was just about doing all the small things right. Then the wall came falling down. Welling up every time I hugged anyone or talked about it.
"It's incredible to be here with this jersey. It's insane. Big thanks to Froomey as well because he committed to me. I appreciate having probably the best stage race rider ever riding for me. It's surreal. It's going to take a while to sink in."
Watch: Tour de France 2018 stage 20 highlights
Thomas came through the first phase of the race, including the Paris-Roubaix stage, unscathed. He dominated in the Alps, winning the La Rosière stage and, the next day in the yellow jersey, the stage to Alpe d'Huez.
He defended the lead through France's south over the Pyrénées, coming under attacks from Primoz Roglic (LottoNL-Jumbo), Romain Bardet (Ag2r La Mondiale) and Tom Dumoulin (Team Sunweb).
Dutchman Dumoulin, who placed second in the Giro d'Italia this May to Froome, will finish the Tour in second place, riding into Paris 1-51 behind Thomas.
"Not until last night really [did it sink in]. As you saw, the last mountain stage was incredible. Luckily I was able to hold it together [in the time trial]," Thomas added.
"Obviously Roglic myself Froomey and Dumoulin were the four strongest. The way Tom rides is super impressive. He's measured and knows his body really well.
"Landa too, the way he rode in the last mountain stage, and Bardet. Chapeau. We were under some pressure there. The main thing was the team won. It's not just about me.
"Alpe d'Huez was probably the most I suffered. That gave me a big boost. The last two stages in the Pyrenees were really hard as well."
Thomas became only the third Brit to reach this point after Bradley Wiggins and Chris Froome. He will also be the first Welsh rider to win the Tour de France.
"It's insane really. It's crazy. Just all the interest from Cardiff where I'm from. It's great to put it on the map I guess. We're a small nation and we just get behind anyone."
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