According to the new Radio Times Spiral 4 starts a week on Saturday after Borgen 2 has finished
One more thing that happens in every series of Spiral is that Pierre's boss gets more and more bug-eyed
That soon? They normally leave a gap between series so people like me can catch up on whatever it is we do on Saturdays, and to spread out the limited stock of foreign dramas available. Perhaps there are enough this year for something every week.