The date on the enforcement notice is 2 weeks ago. So, It was probably issued oin time, but due to the postal strike I didnt get it - your thoughts?

Hi there, all On Saturday 7th I received a letter with a congestion charge fine. It stated that I had to pay the fine before the 4th or it would go up. Unfortuately my time machine isnt working yet, so I guess they will force me to pay the larger amount OR Do I have to pay at all? Isnt there a trestruiction that says fines must be recieved within 2 weeks or they are not valid? Any suggestions would be great. Thanks