Thomas was the fastest around Düsseldorf's 14-kilometre wet and slick parcours. He clocked 16-04 minutes, which was enough to beat the times of Tony Martin (Katusha-Alpecin) at eight seconds back and team-mate Chris Froome at 12 seconds.
"It's still a shock really, it's still unbelievable," Thomas said. "Growing up watching the Tour, watching it after school with my dad. We got Eurosport at home to see it on television. It's amazing to be in it now and on the other side of the cameras."
The Welshman is in yellow by five seconds over second best rider on the day, Stefan Küng (BMC Racing).
"I was just thinking of the Lions last night when I went to bed, now I have my own little lion as well," he added.
The British and Irish Lions upset the All Blacks in rugby this morning; Thomas went to the same school as Lions player Sam Warburton.
"It was an inspiration for me. It was great to watch that, I'm buzzing off of that. That helped take my mind on this,” Thomas said.
"It took the first corner pretty quick and then Nico [Portal, Sky sports director] said, 'Take it easy.' The rest were fast, but I didn't take any big risks. I tried to savour it and get it out all out in the last 4K."
Thomas capped off a successful day for Team Sky, who had four men in the top-10 with Thomas, Vasil Kiryienka in third, Froome in sixth and Michal Kwiatkowski in eighth.
The stage win in the Tour, a first for Thomas, and the yellow jersey, a first for Wales, made for Thomas's the Giro d'Italia disappointment.
"I set the goal of coming here and do the best job here. It was certainly tough, I tried not to watch any of the race. I didn't. I saw the physios in Manchester," Thomas continued.
"Then after five days, out to Monaco and start to ride again. If I didn't have this goal, I'd probably be three to four kilograms heavier and be going slow.”
"Certainly, I was in the best shape I've been. I try not to think about it really. What happened, happened. I move on. This goal of the tour kept me motivated, and I'm moving on."
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