I have how ever had this happen to me in the Landy
The rear outer wheel bearing had worn (badly) this allows the wheel, hub, brake drum and halfshaft to come away.
I was going down hill at the time and the first i knew about it was when i pressed the brake to slow down and it went right to the floor, pumping it made no difference. Landrovers have a transmission brake for a hand brake so there is a drum in the propshaft, so i slowly started to lift that but nothing happened

i was at the helm of a runaway Landy!
The half shaft finally came right out the axle and then i came to a stop with the Landy dragging it's bum along the road, small dribble of EP90 running out the axle. My heart was banging but i was so relieved that i hadn't killed anyone.
I looked back up the road still not sure what had happened and there in the middle of the road is a wheel with half shaft stuck up in the air looking like a lollypop.
It was deffo a brown trouser moment.