What happens when two cars collide with each other head on the downhill of the road?

The first car model is 2009 Honda Odyssey L
The second car model is 2007 Holden Captiva CX V6

The car 2009 lost their control during going down the hill and hit the car 2007
what happen after that. I'm stuck with it can you please give me some information about it or at least give me some website about

What speed were they both doing when they hit?

How can you lose control going down a hill?
Did the driver have a license?
Here in the UK there are lots of hills.
We get as steep as 1 in 3 33%.
The driver who loses control is responsible.