My understanding is that Boris was removed from the flat and went home.
If police attend a suspected "domestic" incident, even in cases where both parties say they are fine, they always ask the person whose property it is if they want the other person to be removed.
It seems that Boris was removed. This, if nothing else, implies that she did not want him there and we do know that she told him to leave and he hadn't gone.
Whilst I don't condone giving the phone recording to the press, I DO think it was the right thing to do to call the police.
Having worked with women escaping abuse and in a refuge, I know that I couldn't sit on my hands and do nothing. As someone else noted, there was another neighbour who spoke out afterwards saying she was just about to call the police when they arrived on the scene, so it's not unreasonable to assume the row was scary or alarming.