The idea that the BBC ever had a left wing bias is totally laughable

Submit complaints. The BBC charter requires impartiality, and they are bang to rights on farage

This now needs to be measured in minutes...

I think your sentiment is completely right, however, a Venn diagram is defined to include all possible intersections, even if they are empty. What you are describing is an Euler diagram. Apologies for my pedantry, carry on.

Former string theorist here! You'll get no disagreement from me on your point, but ignoring the constants does make the calculations easier.