He didn't appear too gullible in this. The impression I got was that he was perfectly aware he was being fooled but was prepared to just keep putting Merlin in the stocks until Arthur got over whatever foolishness he was up to - but that was in the performance not the script I suspect. In the two episodes he comes across as rather over-indulgent of Arthur and rather blind to the danger he has placed himself in by his hard line on magic but not gullible per se.

I rather want to be won over by this series since Arthurian stuff fascinates me - I might see if we managed to record any at any point. I certainly intended to record some.