Complex sentence: Yesterday had to edit the third series' episodes to fit into their timing schedules; therefore instead of them being 60 minutes in length they were reduced to 45 minutes; this was not apparent with the repeats of the first two series.
Split into simpler sentences: Yesterday had to edit the third series' episodes to fit into their timing schedules; therefore instead of them being 60 minutes in length they were reduced to 45 minutes. This was not apparent with the repeats of the first two series.