I wanted to reach through the fog of time and pull these men into the modern world, so they can regain their humanity once more – rather than be seen only as Charlie Chaplin-type figures in the vintage archive film.

[13][14][15] The film's music was composed by Plan 9, a New Zealand trio consisting of David Donaldson, Steve Roche, and Janet Roddick.

They Shall Not Grow Old premiered on 16 October 2018 as a Special Presentation at the BFI London Film Festival, with Prince William, Duke of Cambridge, in attendance.

[19] In the US, Fathom Events arranged special screenings of the film on 17 and 27 December 2018, in both 2D and 3D,[20] and Warner Bros. Pictures released it in New York, Los Angeles, and Washington, DC, on 11 January 2019, with plans to expand to 25 markets on 1 February.

[4] Fathom Events' one-day presentation of the film in the US on 17 December 2018 grossed $2.3 million, setting a company record for a documentary showing.

[23] After Warner Bros. gave the film a general release in 735 cinemas on 1 February 2019, it earned $2.4 million its debut weekend, finishing 10th at the box office.

[26] In a five-star review for The Guardian, Peter Bradshaw called the film "a visually staggering thought experiment", and wrote: "The effect is electrifying.

Through the exhaustive transformation completed by Jackson's team, visages that were all but indistinguishably blurred in the archives take on shape, character and creases of worry, terror and occasional hilarity.

Some critics may object to how Jackson streamlines and elides real events, stripping away specifics while offering no broader socio-political comment on the war.

But as an immersive primer on the first-hand experiences of British soldiers, this innovative documentary is a haunting, moving and consistently engaging lesson in how to bring the past vividly alive.

"[29] Mike McCahill of IndieWire gave the film a B grade, writing that "the filmmaker's extensive restoration project doesn't always provide new insights, but it succeeds at creating a fresh look at the horrors of WWI.

[33] Others have questioned the authenticity of the soundtrack, which was constructed from lip reading and oral history archives and has been given less critical attention than the colourisation techniques.

[34] Historians have argued that, while lip reading may reveal the words that were spoken, it does not necessarily represent regional accents or changes in pronunciation over the century between when the images were captured and the film was made.