The casual but enormous risk taken with this 1989 prank merits its inclusion. In a publicity-stunt-cum-April-Fool-joke, Richard Branson flew across London in a hot-air balloon made to look like an alien spacecraft. The plan had been to land in Hyde Park, where everyone would chuckle and run off to buy tickets on Branson’s new airline, Virgin Galactic
This is what the link in the article is to.
I think they meant Atlantic!
what is a publicity-stunt-cum?
In this case, cum basically means “as well as being.”
https://en.m.wiktionary.org/wiki/cum