Archibald Hamish Lethbridge-Stewart was a member of the Lethbridge-Stewart family who served in the British Army in World War I. He served at Ypres in December 1914 and, following an encounter with the Twelfth Doctor and First Doctor, participated in the Christmas Armistice. (Twice Upon a Time) He was the brother of Alistair Lethbridge-Stewartt and the great-uncle of Brigadier Alistair Gordon Lethbridge-Stewart. (Night of the Intelligence)
He served at Ypres in December 1914 where on Christmas, Archibald was stuck in a crater with a wounded German soldier. As the two men held each other at gunpoint, Archibald stated that he wouldn’t kill the German soldier except in self-defence but recognised that they couldn’t understand each other.
In the moment before they killed each other, Archibald was abducted by the Testimony in order to record his memories. Due to an error in the timeline caused by the First Doctor and the Twelfth Doctor resisting regeneration at once, Archibald was returned to Antarctica in December 1986 instead of Ypres. Archibald became the subject of a conflict between the two Doctors and the Testimony who wished to return Archibald to his own timeat one point, Archibald stated that while he was unafraid of death before, now that he knew he would die, he was scared again.
After the truth about the Testimony was revealed, the Twelfth Doctor agreed that Archibald must be returned to his own time period. However, the Twelfth Doctor requested that he and his predecessor do it as it was their fault that Archibald had been displaced in time. On the return trip aboard the Twelfth Doctor’s TARDIS, Archibald expressed regret that he would never see his wife and sons again.
After returning to Ypres, Archibald was informed that his memory of the entire experience would be erased while a perception filter would keep him from seeing the two Doctors. the First Doctor expressed regret that “the universe generally fails to be a fairy tale”, and Archibald revealed his name and requested that The Doctors check up on his family, (Twice Upon a Time) leading to the Second Doctor’s fateful encounter with his relative Alistair Gordon Lethbridge-Stewart, who would become a long-time friend of The Doctor. (The Web of Fear) After both Doctors promised to fulfill his request, Archibald returned to his spot in the crater, causing time to resume and his memories to instantly be erased.
As Archibald and his German opponent prepared to shoot each other, both men heard Christmas caroling as the Christmas truce began. Laughing, Archibald and the German soldier ended their standoff and Archibald called for medical attention for the man. Watching unnoticed, the Twelfth Doctor explained that he adjusted the time period Archibald was returned to so that it was a couple of hours later when the truce began, saving both men’s lives. the Twelfth Doctor’s meddling in time to save both men caused the First Doctor to finally understand what being “The Doctor of War” meant.
Shortly before the Twelfth Doctor left to regenerate, Archibald noticed him standing on the field and confusedly returned a salute. (Twice Upon a Time)
In an alternate timeline, Archibald and his German opponent killed each other on the battlefield. (Twice Upon a Time)
BEHIND THE SCENES
The novel Night of the Intelligence first mentioned Archibald as the brother of Brigadier Alistair Gordon Lethbridge-Stewart’s paternal grandfather, Alistair Lethbridge-Stewart. However, Mark Gatiss, who portrayed the character in the TV episode Twice Upon a Time, stated that Archibald was there intended to be a grandfather of the Brigadier. This was not denied by Twice Upon a Time’s writer Steven Moffat, but Andy Frankham-Allen claimed that both the Haisman literary estate and Henry Lincoln, who together own the intellectual property to Alistair Lethbridge-Stewart, still consider Archibald to be the Brigadier’s great uncle.