A clip posted by the star on Twitter shows 450 actors personification MPs singing a rousing delivery of The Beatles’ Hey Jude in the House of Commons.
They then extol as Gary Oldman, who plays Churchill, enters the room.
West, who plays former unfamiliar secretary Sir Anthony Eden, wrote alongside the video: “Been watchful to post this for a year. Joe Wright, executive of Darkest Hour, leads 450 MPs in a warmup sing of Hey Jude between takes. Gary Oldman as Churchill creates an opening at the end.”
West also shared a series of photos to applaud the film’s release, including snaps of Oldman’s Churchill at the despatch box and executive Joe Wright.
The domestic cover was recreated at Leavesden Studios nearby Watford. Kristen Scott Thomas, who also stars in the film, told Sky News it was a “very enchanting set”.
:: Gary Oldman’s Churchill mutation in Darkest Hour ‘uncanny’, contend co-stars
The film also stars Lily James, Stephen Dilliane and David Schofield and focuses on Churchill’s doing of the Second World War.
James has oral of the cast’s “audible gasp” at seeing Oldman’s mutation into Churchill.
The role has so distant warranted Oldman, 59, best actor awards at the Golden Globes Critics Choice awards, as good as a Bafta assignment for best heading actor, and the film is also sloping for the Oscars.
:: The Darkest Hour is out in UK cinemas now