Brendan (Ascension of the Cybermen)

Brendan was a Matrix construct, (TV: The Timeless Children) purported to be the adopted son of Meg and Patrick, after they discovered him as a baby in Ireland. (TV: Ascension of the Cybermen) Brendan's story was an analogue for the Timeless Child's, used to hide the true origin of the Time Lords within the Matrix. According to the Spy Master, the Second Tecteun masked this story under a visual filter so that anyone who chanced upon it would find this piece of history to be unremarkable. (TV: The Timeless Children)

Fictional biography
Brendan was found by Patrick abandoned as a baby in a basket in the middle of the road, and took him to his home. While the Gardaí (Irish police) looked for his biological parents, Patrick and Meg looked after him, even celebrating a birthday. After being unable to find his parents, Patrick and Meg adopted the boy, naming him Brendan. Over Brendan's childhood, Meg and Patrick raised him. Brendan attended school, helped his father rake leaves in the garden, and was looked after when he got sick.

As a young adult, he joined An Garda Síochána to "make a difference", and was mentored by the Sergeant. At one point in his service, he chased Michael, a thief, to the cliffs, where Michael pulled a gun on him. Despite trying to reason with him, Brendan was shot, and fell off the cliff, landing on the beach. Despite the seemingly fatal fall, Brendan revived when the Sergeant found his body and continued as if nothing happened. Brendan, assuming his survival was a miracle, received a commendation.

As an old man, Brendan retired from the Gardaí, and at his leaving party, was given a clock as a memento. Outside, he met his father and the Sergeant, neither of whom had aged, and was led into the back office. There, a device was attached to his head, and both Patrick and the Sergeant apologetically told him they would have to wipe his memory, the latter thanking Brendan for his service, before Brendan was torturously wiped of his memory. (TV: Ascension of the Cybermen)

The Spy Master later revealed to the Thirteenth Doctor that Brendan's story, which was a work of fiction, had been hidden in the Matrix on Gallifrey by Tecteun under a visual filter as it paralleled the story of the Timeless Child. The Master had transmitted the story to the Doctor, resulting in her visions of his life. The Master suggested that Tecteun hid the truth in this form as possibly an apology or gift to her child, a way to decode the truth if the Timeless Child - now the Doctor - ever chose. While watching Brendan's memories get redacted, the Doctor noticed that his clock was dedicated for services to the Division, the secret Time Lord agency that operated outside of the non-interference policy. (TV: The Timeless Children)

Behind the scenes

 * As a child, Brendan wears a v-neck jumper with green zig-zags and a red and yellow diamond pattern, which closely resembles the outfit that Sylvester McCoy wore as the Seventh Doctor.
 * Although Brendan's surname and hometown are never mentioned in dialogue, further details are suggested in the scene in which Meg reads a newspaper article reporting on his cliff fall. The article's opening sentence covers multiple lines and is only partially legible, but it identifies the officer as "Brendan Fla-", indicating a second name beginning with those letters (and which, if a surname, is presumably shared by Patrick and Meg). The newspaper's name begins with the word "Western", which corresponds with the script's statement that the town is in the west of Ireland. The article's opening line also mentions "Kilbriain"; multiple real Irish townlands bear slightly different anglicisations of the same name, including Kilbrien in County Waterford and Kilbryan in County Roscommon (though neither are near the west coast).
 * The dates given in Chris Chibnall's script for the Brendan scenes are not literally possible. The script states that the scene where Patrick finds the "six-month-old" Brendan takes place in "Late 1940s West Coast Ireland", specifically 1947; but that Brendan's "first birthday", at which he is 18 months old, also takes place in 1947. Brendan is five years old on his first day of school in 1950, and "8 or 9" in 1951. He is in his "late teens" in 1953, when he joins the gardaí. He gets shot in 1955. Brendan is in his "late 60s" when he retires, but the retirement scene is repeatedly described as "1970s style" and specified to take place in 1973.