Question: "The Darkest Hour" generally refers to the time when Britain was under threat of invasion in 1940 and 1941. Who coined the phrase?

Context articles: Darkest Hour (album)
The Eternal Return (album)
Darkest Hour: Europe '44-'45
Tony Schumacher (British author)
The Human Romance
The Darkest Hour
Deliver Us (Darkest Hour album)
Battle of Dunkirk
The Darkest Hour (film)
Darkest Hour (film)

Darkest Hour is the eighth album by American melodic death metal band Darkest Hour.
 It was released on August 5, 2014 through Sumerian Records.
 It is the first album to feature bassist Aaron Deal and drummer Travis Orbin.
 The album marks the as yet only significant departure from their usual melodic death metal sound, instead having a more mainstream approach with elements of metalcore more prominent, with a more upbeat style.
 They would later return to their familiar sound heard on previous albums on the next release.
The Eternal Return is the sixth studio album by American melodic death metal band Darkest Hour released on June 23, 2009 through Victory Records.
 The album was produced by Brian McTernan (Senses Fail, Thrice, From Autumn To Ashes) who had previously produced Darkest Hour's debut album "The Mark of the Judas" in 2000.
 The album fulfilled the band's contract with Victory, making it their last release through the label.
Darkest Hour: Europe '44-'45 is a free modification developed by Darklight Games / The Darkest Hour Team for Tripwire Interactive's multiplayer first-person shooter video game "", It is based on the Western Front during World War II between 1944 and 1945, depicting the conflict between Allied and German forces.
 Several large-scale operations are covered, including the invasion of Normandy, Battle of the Bulge, Operation Market Garden, and Battle of the Hürtgen Forest.
Tony Schumacher is a British author and broadcaster from Liverpool.
 His first novel, "The Darkest Hour" is an alternate history, set in a 1940s UK after a German Victory in World War II.
 It was generally well received.
 His second book, The British Lion, was released by the William Morrow imprint of HarperCollins, and was also well received in both the USA and UK.
 A third in the John Rossett series of thrillers is expected early 2017.
 He has self-published several other works including "Rear View Mirror: Stories from the streets and the night", recounting tales of his time as a police officer and taxi driver in Liverpool.
The Human Romance is the seventh studio album by the American melodic death metal band Darkest Hour.
 The album was released on February 22, 2011, in North America through eOne Music, and was released on March 7 in Europe through Century Media Records.
 This would be Darkest Hour's last album with drummer Ryan Parrish and bassist Paul Burnette.
The Darkest Hour is a phrase coined by British prime minister Winston Churchill to describe the period of World War II between the fall of France in 1940 and the Nazi invasion of the Soviet Union in 1941, when the British Empire stood alone against Nazi Germany and the Axis Powers in Europe.
 The length of time between the fall of France in June 1940 and the German invasion of the Soviet Union in June 1941 measured 363 days, or 11 months and 28 days.
 It is particularly used for the time when the United Kingdom was under direct threat of invasion; following the evacuation of the British Army from Dunkirk and prior to victory in the Battle of Britain.
 The darkest moment is usually considered to have been 10 May 1941, when over 1,500 civilians died in Luftwaffe bombing raids on London alone.
Deliver Us is the fifth studio album by American melodic death metal band Darkest Hour.
 It was released on July 10, 2007 through Victory Records.
 The album debuted at number 110 on the Billboard album charts, with sales of 6,600.
 "Sanctuary" is featured in the video game, "Tony Hawk's Proving Ground", while "Demon(s)" is featured in "Guitar Hero 5" and "Doomsayer" was made available in "" through the "Darkest Hour Track Pack", the last to be released by Activision.
 The artwork was created by John Baizley who has also done art for bands such as Pig Destroyer, Daughters, and his own band Baroness.
The Battle of Dunkirk was a military operation that took place in Dunkirk (Dunkerque), France, during the Second World War.
 The battle was fought between the Allies and Nazi Germany.
 As part of the Battle of France on the Western Front, the Battle of Dunkirk was the defence and evacuation of British and Allied forces in Europe from 26 May to 4 June 1940.
The Darkest Hour is a 2011 science fiction thriller film directed by Chris Gorak and produced by Timur Bekmambetov.
 It depicts an alien invasion.
 The film stars Emile Hirsch, Max Minghella, Olivia Thirlby, Joel Kinnaman and Rachael Taylor, as a group of people caught in the invasion.
 The film was released on December 25, 2011 in the United States.
Darkest Hour is a 2017 British war drama film directed by Joe Wright and written by Anthony McCarten.
 The film stars Gary Oldman as Winston Churchill, and follows his early days as Prime Minister as Hitler closes in on Britain in World War II (The Darkest Hour).
 Ben Mendelsohn, Kristin Scott Thomas, Lily James, Stephen Dillane, and Ronald Pickup also star.