And despite cosmetic changes to this fifth series - Gwen (Angel Coulby) has become Camelot's new Queen, the Knights of the Round Table are now firmly established in Camelot - Merlin quickly re-asserts what it does best early on in 'Arthur's Bane (Part One)'. There's epic adventure, scenes of derring-do and, naturally, some bromantic bickering between Merlin (Colin Morgan) and Arthur (Bradley James) before the opening titles even roll.
Five years in, this show is now a well-oiled machine. The action scenes are expertly crafted and the show has also struck the right balance with character.
The fan-favourite friendship between Merlin and Arthur, for example, now incorporates both humour and human drama on an equal basis and both sides of the relationship are handled with equal skill by both the writers and actors. At the episode's mid-point, the fun of Merlin impressing the court with his tricks cuts straight to an emotional moment between the pair and it's done with such skill that the transition doesn't feel jarring.
Most of the drama in 'Arthur's Bane (Part One)' comes from a shocking vision of a possible future, in which Merlin witnesses his king struck down by a mysterious figure, revealed at the episode's end to be a now-adult Mordred.
It's too early to judge Alexander Vlahos on just a few short scenes, but bringing a legendary figure like Mordred back into the fold is certainly an exciting development for Merlin and it doesn't hurt that Vlahos bears a passing resemblance to the character's former portrayer, child actor Asa Butterfield.
Let's just cross our fingers and hope that Mordred doesn't end up ingratiating himself into Arthur's court - Merlin has done well in moving beyond some of the clichés that dragged it down a little in the early years and the last thing we need is another Morgana / Agravaine style 'inside man'.
Speaking of Morgana, you won't be shocked to learn that she's the villain behind this week's sinister happenings. Katie McGrath's saucy sorceress is swiftly becoming the equivalent of The Master in 1970s Doctor Who - it's *always* her, so why are our heroes surprised time and again?
Morgana teaming up with a willing warlord is nothing new either, but we'll forgive that since her new ally Ruadan is played by fantastic Irish actor Liam Cunningham (Game of Thrones), who's employing the same cut-class English accent he used to play villains to great effect in films like 2001's Dog Soldiers.
The Morgana / Ruadan scenes hint at what is presumably series five's ongoing story arc - we hear that Morgana was captured at some point after series four's finale and "saw nothing but darkness" for years. We're all for intriguing hints at a broader mythology, particularly as it implies that plot issues not addressed by this premiere - the fate of Aithusa, for one - will be explored in future weeks.
Another point worth addressing about 'Arthur's Bane (Part One)' is the larger role it affords Gwen. We already knew that Arthur was a fair and just king, but it's rather surprising to see the often meek Gwen become a strong, even ruthless Queen, condemning traitorous serving girl Sefa (Sophie Rundle) to death.
Merlin has in the past under-used Angel Coulby, with Gwen often reduced to sitting on the sidelines, politely clapping as gallant knights faced off in yet another bout. But the character's promotion to the throne sees the show finally make the most of this talented actress.
The role reversal of Gwen being waited on, rather than being the one doing the waiting, is also an interesting transition - Coulby does well in conveying the character's slight sense of unease at her new lifestyle.
In terms of performers being well-utilised, it's also great to see Merlin looking to its past and calling its best guest stars back into action, starting this week with Queen Annis, played once again by the reliably brilliant Lindsay Duncan.
There's nothing ground-breaking about 'Arthur's Bane (Part One)', but it's a solid and steady evolution of what we've seen before and that's no bad thing. Merlin has now perfected its formula - it's fun, well-made family adventure at its very best.
