I had artic tailgating me for miles on th a515 , so when I got to double white lines I slowed down until we came to a standstill . I walked round and opened the tailgate and the driver jumped out shouting what was I playing at . I politely replied that seeing as he’d been trying to get in the back for miles I though I should open the door for him . His face was a picture and he dropped back to a reasonable distance .