Initial confusion turned to joy for Dumoulin as he realised he bested Chris Froome (Team Sky) by one second to win the Stage 20 time trial.
"Ah that's crazy! I didn't know anything about the split times," said Dumoulin. "I still thought Froome was one second ahead of me when I crossed the line. Everyone was saying I was second by one second."
"I has such a hard time yesterday, and all my frustration came out at the finish. Today I cannot believe this. It’s amazing. One second...!"
Dumoulin revealed he was on edge for most of the day after he couldn't find his world championship time trial skinsuit, specially designed for the Dutchman to reduce aerodynamic drag.
The factory that manufactured it is located just 45 kilometres away, over the border in the Spanish Basque region.
"What an amazing last day. I was so nervous. This morning we found out we lost the skinsuit, so Exteondo, our sponsor, they’re from the Basque Country on the Spanish side and they made a new one - they were sewing it this morning! I'm forever thankful because otherwise I wouldn't have been finishing in this beautiful world champion's jersey."
"I always give some stuff at the beginning of the Tour to the bus or the truck so that I don't need to carry it around for three weeks," explained Dumoulin. "My bag was with all my skinsuits and everything got lost. They actually made it, because they are in the Spanish Basque Country, and it was crazy. It's all good now."
Dumoulin reflected upon the day's performance, saying it was a surprise after not feeling on top of his game on previous stages.
"I didn't expect to have these good legs on the last day, I was struggling these last few days actually. To top it off with a win and the second place on GC, it's amazing really."
Dumoulin is all but guaranteed a second-place finish in Paris, making it two in a row for the big Dutchman after the Giro d'Italia in May.
"Geraint Thomas is an absolutely deserved winner," said Dumoulin, "he nailed it from start to finish. He was the strongest and didn't make one mistake. Big congrats to him. I'm just super happy with my second place."
When asked if he would focus solely on the Tour next year, Dumoulin hedged a bit.
"Probably yes, but it depends on the parcours (race route), if the Giro has a nicer parcours, I go to the Giro."
The 2018 Tour de France concludes with the traditional final stage in Paris. Coverage starts on SBS from 11.30 pm, also available via the SKODA Tour Tracker App and streaming on the Cycling Central website.