You are do right. I did it once to a lady boss who was winding me up with her high heeled stockinged foot under the table at the office Christmas meal.
All the time she was sat opposite me grinning away.
She had open sided shoes on and it was a noisy function room so I thought what the hell. Grabbed her ankle scraped the inside of her stretched arch.
What I was expecting was a little reaction and a giggle.
In beknown to me she's about 11 out of ten on the foot ticklish scale. What a, scream she let out followed by, don't I'm really ticklish. The. AhhhHa haaa. As I fave her instep another scrape.
The only person who heard over the drunken noise was my work mate sat next to me who looked and laughed.
I got the impression he thought he'd missed an opoertunity lol