Yes it seems like it's open to abuse from both sides really, as it certainly wasn't me that removed the first two tickets. Anyway it's not my job to devise a fair system and I'd just like to minimise the damage of what has turned out to be one costly mistake on my part.

Thanks Jamberson. I'll give option 1 a go. Green_n_Mean - yes that is pretty obvious thanks, but the NTO's are sent after the 14 day discount period so I would unfairly have to pay £130 per ticket instead of £65.

I parked in a residents permit bay on an sunday in Islington when it was free and went to work. Unfortunately I rarely drive to work and forgot I'd brought the car and headed straight for the tube after work! Duh! It wasn't until Saturday that I realised my mistake and went back to retrieve the car. I had three PCN's on the windshield which I paid within a week at the discount rate. However I have just recieved 2 NTO's for tickets that weren't there! How am I supposed to pay them if they aren't even there? Just to be clear: there were 5 days of fineable parking, but there were only 3 tickets present that were dated for the last 3 days. The NTO's are for tickets supposedly issued on the first 2 days but seem to have been removed. Also is there a maximum number of tickets that can be received in this situation? Any advise would be most welcome.