It was definitely after vlogmas/Cornwall that they changed. I remember in the changing of the name video they did actually say they had talked so much about the channel etc and Mark said "I've actually said what I feel for a change" so I reckon the convo went something like this:
N: things are going good at the minute aren't they Mark!?
M: No actually Nads they're NOT, one feels that the channel is all about YOU! I do ALL the editing so I want my name in the title too!
N: ok darling I'll rescue you and let you have your way
M: good. Also because I haven't really got a proper job I'm going to start charging those gullible morons £1.99
N: yeah that's a good idea! I'll make promises I can't keep just to keep reeling them in and I'll also make mamas spaghetti because I really don't think I've made it enough.
M: and I'll buy 65 masks so I can wear one in each video and scare people
N: (places hand on chest, pauses) your SO intelligent Mark, well done baby
M: I know I am. You don't get to be a journalist, stock broker, writer, director, film producer, teacher, photographer, entertainer, camera man and just a general smart ass without being as clever as ME!