A robot dog built to last a single “Doctor Who” story instead spoke for decades, in the clipped voice of an actor who has now died.
John Leeson, the British actor who voiced the robot dog K9 on the BBC science-fiction series “Doctor Who,” died Sunday, Nov. 1, 2026, at 83. His son, Guy Ducker, 54, a film editor, announced the death on Facebook.
“I regret to announce the death of my father, John Ducker, a.k.a. John Leeson, at 3.03pm today after a summer of illness. The end was peaceful,” Ducker wrote.
Ducker thanked the “Doctor Who” community for the support given his father’s work over the decades, and he ended the announcement with a line from “Hamlet”: “Good night, sweet prince…”
Tributes From the Doctor Who Family
Russell T Davies, the former “Doctor Who” showrunner, led the tributes on Instagram, calling K9 “a posh dog, uppity, haughty, wry, but somehow innocent too, and so funny.”
His wife, Judy, and his son, Guy, survive him.
Built for One Story Only
K9 made its debut in the 1977 serial “The Invisible Enemy,” alongside Tom Baker’s Fourth Doctor. The writers Bob Baker and Dave Martin had created the character, a machine with a laser in its nose, for that story alone.
Producer Graham Williams and script editor Robert Holmes saw the appeal, and Leeson’s performance was a factor in a one-off prop becoming a recurring companion with a reply generations of viewers can still recite: “Affirmative, Master.”
On All Fours in Rehearsals
Leeson’s clipped delivery worked as comic timing rather than mechanical monotony, and his dry confidence played against Baker’s unpredictable Doctor. During rehearsals he sometimes moved around the studio on all fours, so the other actors had something to play against.
He once described K9’s personality as “pedantic arrogance and perky one-upmanship.”
He voiced the character throughout Seasons 15 and 16, according to Big Finish Productions, then declined to return for Season 17, when David Brierly took the role. Leeson came back for five serials in Season 18, and K9’s regular appearances in the series ended in 1981.
The part kept finding him. He returned for the 1981 spin-off pilot “K-9 and Company,” which starred Elisabeth Sladen as Sarah Jane Smith, and again for the 1983 anniversary special “The Five Doctors.” He reunited with Sladen in the 2006 Tennant episode “School Reunion” and worked with her again on “The Sarah Jane Adventures.” He voiced K9 in “Journey’s End” in 2008, and the audio dramas continued in Big Finish productions as recently as 2025.
From Hospital Porter to RADA
He was born John Francis Christopher Ducker in Leicester on March 16, 1943, the son of a clergyman. As a young man he joined the Leicester Drama Society, and he worked as a hospital porter before entering the Royal Academy of Dramatic Art in 1962, taking Leeson as his professional surname.
Leeson built his career in repertory theater. He played the original Bungle on the ITV children’s series “Rainbow” in 1972, and his other television roles included “Dad’s Army,” “Blake’s 7,” “Crown Court,” “The Bill,” “Doctors,” “Sorry!” and “Longitude.” He also spent time as a continuity announcer for Channel 4.
Earlier in 2026, he played Dr. Watson opposite Tom Baker’s Sherlock Holmes in the audio drama “Sir Sherlock.”