Someone asked me this in one of my classes today.
The accent they mentioned is the Transatlantic or Mid-Atlantic accent, very common in movies from the 1930s and 1940s. It was also common among American heiresses married into aristocratic British families. I sometimes have a bit of an in-between accent myself. My South African accent has become milder over the years of not being surrounded by South Africans, and I also have to have a neutral accent when I teach, to prevent all my students from learning to speak English with South African accents.
The one that surprised me is Matthew Rhys in The Americans, he’s from Cardiff South Wales and when interviewed he speaks with a distinctive Welsh accent. Yet never a trace of it in the six seasons of The Americans where he plays a Russian KGB agent living in Washington DC alongside his ‘wife’ played by Keri Russell.
Quite a talent I think.
My own accent is much diluted compared to how strong it used to be!! If I went home for a few days it would come back again!
Yes that happens to me too – two days with my family – who have very strong Saffa accents – and I sound just like them! I have to admit to not being a fan of the SA accent. Maybe we all have a weird relationship to our own speaking voice.