Spencer Pemberton

 was a second lieutenant in the Parachute Regiment, 3rd Battalion during the Korean War, where he met and mentored a young private called Alistair Lethbridge-Stewart. He was instrumental in instilling in Lethbridge-Stewart a desire to become an officer. He became known to those under his command as "Old Spence". (PROSE: The Ambush!)

By the late 1960s he and Lethbridge-Stewart were firm friends, and when the Special Forces Support Group (1 PARA) were sent in to deal with the London Event, Colonel Pemberton requested Lethbridge-Stewart's help — he was promptly brought in from Libya. (PROSE: The Ambush!, The Forgotten Son) Pemberton died at the hands of a Yeti. Captain Knight served under him for some time, and considered him a good commanding officer. (TV: The Web of Fear) In an alternative timeline, Pemberton never died and continued to lead the fight against the Great Intelligence, but was convinced to put time right by Tess, a manifested form of the TARDIS. He saved Lethbridge-Stewart at Tooting Bec, and felt time resetting itself as he faded away into nothing. (PROSE: Legacies) His body was interred in the mortuary of St Mark's Hospital in Kenton during the clear up after the London Event, alongside other soldiers such as Captain Knight and Staff Sergeant Arnold, and later buried with full honours. (PROSE: The Forgotten Son) Lethbridge-Stewart visited Pemberton's wife, Joan, and their adult son, David, to inform them of Pemberton's death, wishing it had been him who had died instead. (PROSE: Legacies)

Behind the scenes
The character was only referenced on TV in The Web of Fear, and was named after script editor Victor Pemberton.

His full name was given in The Ambush!, and author Andy Frankham-Allen stated on his blog, "As a tribute to Pemberton's life-partner I christened the character with the full name of Spencer David Pemberton (Victor's partner was actor/producer David Spenser, who died in July 2013)."