of exploration? Imagine an entire 13-part run that delved into the aftermath. Could the King ever trust his manservant again? Would he willingly conceal his secret? And how would it affect his feelings about magic in a broader sense?

Even putting plotting issues aside, the decision to wrap up Merlin at the end of this year would seem odd when the show's still-formidable ratings are taken into consideration. Since it launched in 2008, the show has consistently pulled in 6-7m every single week - that's a phenomenal achievement, particularly when one takes into account how audience figures in general are on the decline thanks to online viewings, personal video recorders and the like.

Watch Bradley James (Arthur) discuss the third series of 'Merlin' with DS in 2010:

What's more, Merlin isone of the few weapons that the BBC has in its arsenal capable of fending off the Saturday night assault of The X Factor - those 6-7m numbers seem yet more spectacular when you consider that the show's scheduled opposite ITV's reality TV singing contest behemoth.

But, for the sake of argument, let's take a look at the flip side of the coin. Merlin was always intended to run for five years and it takes guts for the show's producers and the BBC to wrap it up when it's still creatively strong rather than let creative decisions be dictated by their wallets.

Watch Colin Morgan talk about 'Merlin' series four in 2011:

One only has to look at US drama Supernatural to see how quickly and drastically a show's quality can