This also included a new 13 pin socket. Following fitment of the new Towbar a dashboard warning light came on , Which now constitutes a MOT failure as advised by Mercedes by email.
The car has been on the Star machine and Mercedes advice the only way to remove the warning is to switch off the Towbar electrics which then disconnects the wiring to the new socket.
It appears the company that fit the Tow bar used the existing wiring from the old socket and wired the new socket with this wiring, as I understand nothing else was changed