Knocking sound when braking

[Lukea]

Morning,

I picked up my new car on Friday, it's a 2012 vrs estate (tdi dsg). I've noticed that when braking from higher speeds (70ish ) I can hear a knocking sound from the rear left. It sounds almost as though the ABS is kicking in. Any thoughts as to what this could be? I'll be going back to the dealer next week but if like to go with a bit of knowledge if possible! I have had a look at the disc which doesn't have any obvious marks on it.

[WesternDuke]

A loose stone guard perhaps? I had this on a Mark 5 Golf.

[Lukea]

Thanks I'll take a look!

[Lukea]

Rear disc is knackered!

[Aspman]

Rear disc is knackered!

 

Has it split through the middle?

 

Someone posted that here before and it ended up with VOSA.