Mispronounced words.

It’s not slang. It’s the very top strata of society.

It’s a test to see who is posh and who isn’t.

An outsider is caught out straight away.

I listened again and this time I heard it plain as day. How strange, I could almost swear they changed it.

Awry
Secretary
Sewerage (when what is meant is 'sewage')
Wednesday

Mobile

It means able to move, a Calder sculpture, or a city in southern Alabama.

The Alabama city and The Calder sculpture are both pronounced Mo'-beel.

The adjective used to be pronounced mo'-bl, but now you often hear mo'-bile, bile rhyming with Nile.

Over here it's pronounced so it rhymes with Nile.

It's shorthand for mobile phone.