Warning: Full reviews contain spoilers for those who have not yet seen the episode. Updates will be made as more reviews come in.
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Den of Geek "Bradley James continues to sparkle as the more responsible Arthur, delivering lines with decent comic timing and showing palpable emotion during the scenes with Uther. His banter with Merlin raises a smile, as it always tends to, though there are times when the scripted dialogue does seem a bit forced as the writer tries to get to the point or set up a witty comeback. Thankfully, James and Morgan remain a charming double act and it's hard not to like them both."
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Radio Times "But fair play to the writer (Misfits creator Howard Overman), whose story spells out that there aren’t always quick fixes and easy answers - doubtless a constant temptation in a family show about magic."
Daemon's TV "It was a brilliant episode, with some really lovely directed moments...and some very intelligent moral twists. After last week’s mediocre episode, this one was Merlin back on top form."
Geek Syndicate "We have yet to see what the rest of the series holds, but this episode is right up there with one of my all-time favorites from Series 2, The Sins of the Father. There’s a delicate balance between comedy and tragedy - it’s a fantastic effort done beautifully by Bradley James, who delivers his strongest performance to date and Colin Morgan’s understated yet emotionally charged turn."
Clique Clack "This episode belongs heart and soul to Bradley James and Colin Morgan. In an episode where they both easily could have strayed into exaggerated expressions of anguish and over-use of histrionics, they instead turned out performances that were contained, mature, and spoke volumes about their characters and their relationship far beyond what the very sparse text explicitly stated."
Dan's Media Digest "I was surprised "The Wicked Day" was written by Howard Overman. He was one of the show's best writers in its early days, and it's nice to see he's still willing to return for the occasional episode since his career took off with Misfits, but I expected something a little better from him."
Dork Adore "To be honest, I feel the BBC tricked me with this episode of Merlin. I was prepared for upbeat fun after last week’s dark sobbery, but that wasn’t what I got at all. In some ways, this was an even bigger downer. Which I will be spoiling, by the way, so don’t read on if you don’t want to know. Does this mean Merlin has finally come of age? Or, worse still, is this the angry puberty of the show?"
Critictoo "After two gloomy episode, The Wicked Day promised to be more jovial with the festivities for the anniversary of Arthur... This is the first episode of a surprise in store for a much greater importance."
SFX "Naturally you expect great things when you see that Howard “Misfits” Overman has penned an episode. And this doesn’t disappoint. In the past, Merlin has been accused of hitting the reset button every episode, with no real progression for the characters or the legend - but “The Wicked Day” changes the central relationships completely."
Digital Spy "'The Wicked Day' must have been a difficult episode of Merlin to get right, but the writers come up trumps. The balance between humour and pathos is just right..."