“How did they get it to leak oil?”
As the owner of a number of antique British cars, this is a bit of a myth. It was extremely common in English cars to have an active rustproofing system that used a continuous stream of oil to lubricate and protect the undercarriage.
If the car sat around a lot, this would then drip. If driven frequently, it was fine.
Americans tended to use British cars as weekend toys, so they “leaked” more.
Well, my Spitfire was a daily driver, and it leaked a bit...