Ah, I was thinking of the election rules where they are required to give a representative amount of time to each party, not the impartiality rules which, frankly, are vague to the point of uselessness.
The classic example of BBC lies would be Nick Robinson of course: https://www.youtube.com/watch?v=K_XhTALHQzI
If you want a more recent example of BBC bias, try: https://wingsoverscotland.com/the-bad-losers/