Surname Length

[manwithaplan11]

Does anyone know the max number of characters allowed for a surname? I know for a first name it's 15 so I assumed the surname was 15 as well, but recently saw someone's that was 18 letters long.

I would test this myself, but I'm not sure if I can change my surname then change it back again, for some reason on live I remember you having to petition to change it. Or am I remembering this wrong?