ran into the back of another driver

Hi, on my way to work early in the morning, I hit the back of the car in front of me. I accept that its my responsibility to avoid this by leaving enough of a gap etc. However, Ive got film footage from my phone cam of the accident which shows:

1) The car in front was tailgating the car in front of him, and was constantly touching his brakes
2) When the car at the very front turned left off the main road onto a slip road, the car which was following him pulled up along side - perhaps to have an altercation.
3) Just before impact the middle car (which I hit) had decided to turn left as well - (his indicator went on) and as a result of the collision his car veered immediately to the left.

In the minute or so before the collision we were all doing about 40 to 50mph down a steep hill in damp and very dark conditions, and I think that as we approached the junction I was probably doing about 40. Although I braked hard I ended up shunting the car at maybe 10mph.

Is the other driver in any way liable for stopping in the middle of a 60mph zone to have an altercation with someone he was tailgating?

I dont know for sure, but due to the conversation which followed I think that the other driver's destination didn't require him to turn off - perhaps reinforcing my suspicion that there was some sort of altercation.

Any advise appreciated!