[Shasown]

Channel 4 are run commercially, they make money by selling the time in commercial breaks to advertisers, therefore if a series has more viewers the time slots in and around that program are worth more than less watched programs.

When they sell advertising slots its normally on a weekly case, though they do allow longer agreements with bigger payers. Sponsors of programs pay higher premiums and get the privilege of having their adverts immediately at the start and end of the program and also the start and end of the commercial breaks.