It was on the M20 between J8 and J9. Reg started RX62.
The car had just finished dealing with a van that stopped on the hard shoulder and pulled back onto the motorway a hundred metres or so ahead of me.
The lights weren't that subtle after they were turned off (either side of the rear number plate) but could easily be missed. There was also something in the middle of the rear bumper but I couldn't make out what that was.
Just thought I'd let you know 