osoba dobrze poinformowana in English:

The insider trading scandal put a lot of people out of business.

The politician tried to cover up the insider trading.

His books have made him an insider in the music world.

‘The move has been welcomed by party insiders as well as other political organisations.

The article was an interview with an insider, a real authority on the Bosnian situation. A man called, he said he might have some insider information on the situation.