Nice loud rattle on the way home last night
Turns out my heatshield over the back box thought it was time to fall on the exhaust.
Why are all heatshields so bad for corroding away. And the fixings so rusty, two sheared off, so now got two stainless bolts going through from inside the boot. Nice of the stud to leave a perfect M6 hole in the body.
Some large penny washers and it should last another 10 year or more.