So...this ole man is a wee bit confused. Like I said, I'm old...so...humor me.
If I read your post correctly, I'm assuming "arrive" meant exactly that; the couple WENT TO/ARRIVED at the prom in the '40???!
If so, howdehdodat??? How in the world did the young lady manage to maintain her dignity getting in and out of the car in a prom dress?! Seriously! I really have no clue how that might be accomplished! Obviously there must be a way...but, I haven't the foggiest clue as to what that "way" might be! Forgetting that for a moment - how/where the devil did she manage to find room for both herself and her gown once inside the car! (I'm assuming a "prom" in the U.K. is the same as a "prom" on this side of the pond? 'Couples arrive and depart together?)
Given the mode of transportation, I'm thinkin' arrangements must have been made for her to change into her gown once AT the prom...either that or prom dresses these days aren't anything like ones worn by young ladies back in 'my day'...you know...back when dinosaurs roamed the Earth?:
^^^You can see why I asked...
Edit: These are supposed to be circa 2017. 'Pretty much the same issue(s):
Sorry Larry, grandson Louis did not have a lady to go with, so decided to do one better and arrive un? noticed to the assembled throng who were posing in all sorts of motorised vehicles, but he was the only one to arrive in a full blown race car on megaphones, and on the public highway ! They heard us coming from a very long way off ! I just got to chauffer him there.