Decided to remove the black plastic from the rear of the car to check how to get to parking sensors as I have a strange problem with the camera packing up and it has now thanks to the dry weather proven to be when it rains non stop like it had been doing as fault has now gone away. Behind the black plastic I found lots of road dirt trapped also up behind the back box and the near side wing where the other back box would be if it had one. So I banged on the rear wing sections with my hand and out dropped a staggering amount of dirt/mud, god knows how long it has been there but in total it weighed in at 15Kg yes I was shocked so check yours today especially if like me you live in a rural area and have to drive down narrow roads frequented by farmers. 

Seen this fault before in a jaguar forum, will try and find the related article.