My experience was with a well known British Labour Politician , lets just go with Peter M ......
i was flying Qatar, London - Doha , i had rebooked 1 A , when i boarded i noticed someone was in my seat , when i asked why , the said passenger told me " Please talk to the crew , this is my favourite seat , I am sure they will find you an alternative "
I knew the land side manager from flying every week for the last 6 months, so i had a word , as the CC could not do anything as he had VVIP next to his name apparently, the manager asked for his boarding card , which was in 5D , after another 10 mins discussion which included the said person saying "surely this passenger can move to my seat " obviously thought that possession was 90% of the law" finally he did move , not a word to my face and spent the rest of the flight refusing all contact with CC including food and drink.
If he had a decent reason or had actually been polite i may have moved , but sadly he had neither