BBC demand I delete footage then cry to the police

I was taking some photos around Cardiff bay area and found the BBC studios building I had been looking for.

I understand that people don't like it when people have a camera but the response I had from these security goons are awful.
I tried to explain that I can take videos or photos but he was so sure that I couldn't they called the police.

To think that a company that films everything from peoples entrances to making movies and TV shows do not know the laws of photography.