Seventy-five years ago a battle began: it was over within three months.
For our Geo Quiz, we want you to name the building where the battle took place.
Now, it's not what you think. This contest was between competing television systems, conducted by the BBC.
In Studio A was the Marconi-EMI system. In Studio B, the Baird system.
In the end, Marconi-EMI won out.
So can you name this building on a north London hill where the world's first TV service — high definition in its day — was created?
The answer is the Alexandra Palace sitting high on a hilltop overlooking London. 75-years ago Wednesday, the palace played host to the start of the world's first regular television broadcasts.
The World's Laura Lynch reports