During the making of Stanley Kubrick‘s Dr. Strangelove (1964) Peter Sellers did a series of phone interviews to promote the movie and demonstrated his amazing ability to mimic British accents:
If you are wondering why he is doing this in make up and costume, back in the 60s actors would give generic answers to pre-scripted questions.
They were actually talking to someone on the set and the media outlet would then edit these into the final interviews.
> Peter Sellers at the IMDb
> Find out more about Dr Strangelove at Wikipedia