400 Fuel filler cap broke

[M4rk 160]

I never normally let my car get too low on fuel but I was driving back from a meeting in my 400, fuel was getting very low but I knew where I was filling up so not a problem...or so I thought!  Pulled in to the garage only to find when removing my fuel filler cap it broke.  It was feeling very tight and when turning I knew something had failed and then the black top part of the filler cap separated from the main body.  Slightly alarming moment for me given how low the car was on fuel.  A quick call to my local dealer who gave me some advice but I had no tools to try the fix they recommended.  Walking around the garage forecourt wondering who to approach for some tools, I happened to see a tyre fitting garage behind the petrol station, so popped over there and sure enough they were able to help.  In the photo, the white mechanism broke off easily, to leave the inner sleeve of the cap, he managed to use some bent-nose pliers forced open in the sleeve which managed to grip on enough for it to be undone - it took quite a bit of force.  I didn't catch a pic of this moment because I was more concerned about the pliers slipping and me ending up with a decent scratch in the paintwork!  This allowed me to get enough fuel in to drive the car to the dealer for a new cap to be fitted. 

The dealer said that they have not encountered this issue before so it seems like I was unlucky and this is a rare fault.  I thought I would share though, in case anyone else has the same problem.  My next purchase will be some decent bent-nose pliers for the boot! 😀