There is a particular kind of actor who seems less like a person and more like a being summoned from the margins of an illustrated manuscript, and Anya Taylor-Joy — all crystalline cheekbones and other-worldly stillness — belongs entirely to that category. It came as little surprise, then, when the Hollywood Reporter confirmed this week that she has been cast as Seren, a Sindar elf described as a "trusted, lethal agent" of the elvenking Thranduil, in The Hunt for Gollum, the forthcoming film to be directed by Andy Serkis, who will once again inhabit the gurgling, ring-haunted creature at the story's centre. The production, on which Peter Jackson serves as producer, reassembles a company that feels both familiar and slightly spectral: Ian McKellen returns as Gandalf, and Lee Pace reprises the imperious Thranduil he first played in Jackson's Hobbit trilogy. The film concerns itself with a chapter of Tolkien's legendarium that the author himself dispatched in barely a handful of pages — the years-long pursuit in which Aragorn tracks Gollum across the wilds of Middle-earth before delivering him to Thranduil's cavernous halls in the corrupted forest of Mirkwood, where Gandalf arrives to conduct his interrogation.

Tolkien's economy with this episode was, one might argue, entirely deliberate: it is connective tissue, not a story in its own right, covering nearly two decades of events that exist chiefly to explain how Frodo came to be entrusted with the One Ring. That Serkis, Jackson and their collaborators have elected to expand it into a feature film raises questions that no casting announcement, however luminous, can fully resolve.