Knocking noise from rear on starting

Hello, I'd be grateful for any advice you have on the following.
We saw an 04 Freelander TD4 and took it for a test drive. As we turned it on we heard a knocking noise from the rear of the car and I wondered whether anyone could suggest common issues we could check for?
Thanks very much

Probably the exhaust hitting something because one of the rubber holders has perished or the pipe has been bent by an impact. Get underneath and give it a wiggle.

Yes, it's the exhaust hangers. Passenger side just behind the bumper. It's probably dropped off.
Mike