Detectorists' Mackenzie Crook unpacks Christmas special's big twist

As well as being writer and director, Crook also stars in Detectorists as Andy Stone, a dedicated member of Danebury Metal Detecting Club alongside close friend Lance Stater (Toby Jones).

He spoke to Radio Times about the stunning note on which this latest – and probably final – episode concludes. Be warned that full spoilers follow for a reveal you don't want to miss out on.

The latest episode focuses on a sizeable and as-yet-undetected plot of land that Andy and Lance get permission to search, which brings out a selfish streak in the latter when he discovers gold.

Lance tries to keep this under wraps for as long as possible – after all, the best that Andy had found was a dirty old clay cup – but inevitably, word gets out and a full professional survey ensues.

At a press conference in London some time later, Lance hears that his gold fragments are suspected to have belonged to an ancient box used to transport an item of unimaginable importance: the Holy Grail.

The historian leading the briefing remarks that the long sought after artefact would most likely have been a "simple clay cup", sending Andy and Lance into a sudden state of panic.

Could it be that the cup they had so carelessly abandoned in the scout hall – since cleared out and renovated – is arguably the most famous missing treasure in human history?

Though he doesn't view himself as religious, Crook has always been "fascinated by the story of Jesus", he tells Radio Times, and that long-standing curiosity is where this mad idea came from.

"I believe there was a man, historically, that did some of those things, so I have always had in my head the idea of the Holy Grail and that was obviously just a cup, any old cup," he explained.

"What if it had somehow survived and ended up in a charity shop or something? That was the incentive to do it. It’s about treasuring history rather than faith and religion."

At a press event for the episode's launch, Crook said that for "20 years or more" he has imagined a story for how the Grail could have "survived and got to England" – a journey that begins with the intervention of an innkeeper's daughter in Jerusalem.

"So that's something I've been wanting to do for a long time, and I was able to crowbar it into a Detectorists plot," he explained.

As for whether it is the real deal, Crook said that "it might not have been" but also referenced a moment of "magic realism" in which Russell (Pearce Quigley) turns up to the club rejuvenated after drinking from the cup.

The signs are certainly there, if you're looking.

This feature-length special also marks the first time that Detectorists has filmed scenes outside of the UK, with the crew travelling to Bulgaria for a sequence set in biblical Jerusalem.

"They’ve got a big standing set – a whole Roman city – that various productions go and film at, so we were able to find backstreets within this set that could double for old Jerusalem," explained Crook.

"Although audiences love the familiarity of Detectorists – because this is a special, I wanted this to be lifted at least in some way to make it stand apart from the rest; to make it a bit more cinematic and a bit bigger."

Detectorists is available to stream on BBC iPlayer. Check out more of our Comedy coverage or visit our TV Guide and Streaming Guide to find out what's on.

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