When American actors try to do a British accent they often worry more about the accent than what their lines mean. This makes their accent stand out as it is the main thing they give the audience (or a casting director) to listen to!
Even when an accent is perfect the audience does not care about it for long, what matters to them is if the actor is funny / scary / charming / shy / bossy, or interesting.
Coaching a British accent may be needed to avoid obvious, like pronouncing “tomato” in the American way – “tomAIDo”. But all that is needed with a British accent sometimes is not to sound American! An audience will accept that a character is from the UK just because that’s where the play takes place, and what makes the accent more convincing is having a British attitude about everything.
To start with, actors may feel more British if their character can sometimes be polite and to have ‘good manners’ in difficult situations.
Then a British accent may sound normal, and actors should realize that if they think their accent isn’t perfect that somebody somewhere in the UK probably talks like them, – because there are so many different UK accents, and the audience may just accept that your character has spent some time in the UK and some in the USA!
I have coached some actors who were in a hurry, and who ended up speaking with just some of a Cockney accent, or smart London, or Northern, Welsh or Scottish accents, and the actors have just been guessing the accent, but it was enough to satisfy directors and casting offices who only wanted to see if the actor made their lines interesting.
Actors must work out the subtext of their lines. The words “I love you” may really mean “Do you love me”, and the words “I’m tired” may mean “I want you to be left alone!” Al lines have to be worked out!
Politicians and priests also often repeat their speeches, but – since they are not trained actors – they have no feelings to keep their words alive. This may be why a politician gets no votes, or why priest has an empty church. They are repeating words in the same tone of voice for hours! Actors cannot just repeat their words, they must have a reason for saying them which is important and matters to them.!
In a famous 2023 film, an actor using an accent that we all knew was not his own, says to his girlfriend “I’ll see you when you get back”. The audience all guessed, with sadness, that the character was lying, and had no intention of coming back. But, then, after pausing, he said exactly the same line again, to the same person, and the audience realized he was intending to propose marriage when he “gets back”. I have never heard anybody comment on the actor’s poor accent!