Mulsanne exhaust rattle

[Davetherave95]

A few weeks ago I noticed a rattling coming from the left exhaust of my 2013 mulsanne at idle revs. I took it to the local dealer who said some small stones had worked their way into the exhaust tail pipe, which they removed. It was fine for a week but unfortunately the rattle has now come back. The car hasn’t really been used, so I’m not convinced it’s more stones.
Has anyone ever had a similar problem or have an idea what might be the problem. It sounds a bit like small nails rattling inside the exhaust!
Cheers

[escort 1983]

It could be the butterfly flap in the rear exhaust rattling. I would try holding the valve to see if it changes the tone or stops completely. Does it get quieter when warm?

[Davetherave95]

The noise is the same at all temperatures. I can try that, how to I hold open the valve?
Cheers