This happened 4 years ago (40s & married). If cheating is an issue for you, best to move on. I travel internationally for work a fair amount. I had meetings in Paris and decided to stay the weekend to visit Normandy/D-Day historical sites. After researching a few tour companies, I booked a full-day tour then planned on taking the train back to Paris to attend a concert on Sat night.
We load up in the van. We’re all yanks, but I’m the fifth wheel as the other 4 were two couples traveling together. So, naturally I get shotgun up front. Our guide spoke English quite well as she was a college student (~23-24) working as a guide in the summer.
I speak decent French. The others did not. This came in handy later. During the tour, I harmlessly start to make her laugh a bit. She’s good fun and we all enjoyed the banter in the van. When we’d stop to get out and walk the site, she’d tell us about the significance etc then let us take pics or investigate the area a bit. Since I was on my own, she’d tag along with me. We’d chat and flirt. I took reasonable opportunity to touch her. I’d put my hand on her lower back when I wanted her to walk ahead of me (fab view climbing stairs behind her).