To be feeling cross about this?

[Suncreamandspades]

A relative was giving us a lift last week. At the round about a car tried to cut us up undertaking. Relative didn't let him. No issue.

Other car was then pissed off so drove up the backside of the car we were in for a while. Relative got angry and slammed on the cars breaks to 'scare' the car on his bumper who was driving aggressively and almost crashed into us.
My kids were in the back and its made me quite cross Tbh but I don't know if I am over reacting. The car could have very easily gone into the back of us although we were only going approx 40 mph

They were both bu. The other driver was a dick but you relative shouldnt have reacted.

In advanced driving leasons you learn about defensive driving, which means driving safely even in situations like this.

I'd probably be declining their kind offer of a 'lift' in future.

FFS, I might let off steam by muttering darkly about bad driving, but wouldn't dream of responding to it like that - that's just dangerous and risks delaying you all massively (presumably partly why the relative refused to be cut up in the first place).

No more lift from this person, if you can help it!

No more lifts (sorry)

I would be annoyed and also have dealt with it at the time. Rather being cross for a week.