The Highlanders was to be the last purely historical Doctor Who story until 1982's Black Orchid.
Although commissioned to write this story, former BBC Head of Series Elwyn Jones didn't write a single line of it. Due to his other commitments, the scripts were actually written by story editor Gerry Davis, who was given a co-writer's credit on the transmitted episodes.
Jones's outline for the serial, originally titled Culloden, was loosely based upon John Prebble's 1961 book of the same name. Davis's completed scripts drew more from Robert Louis Stevenson's Kidnapped.
Jones continued to write for numerous other television programmes, including Doomwatch, until his death on May 19th, 1982.
The Battle of Culloden was the culmination of a struggle between the English throne and the followers of Charles Edward Stuart, known as Bonnie Prince Charlie. Charles had been forced out of England in 1688, but was determined to restore his father to power.
He won the loyalty of clans dwelling in the Scottish Highlands, who began moving toward England in the summer of 1745. The clans were eventually confronted by the Duke of Cumberland, whose troops won the decisive clash at Culloden Moor near Inverness on April 16th, 1746.
Frazer Hines was chosen to play Jamie McCrimmon, at the recommendation of BBC Head of Serials Shaun Sutton. Hines had enjoyed a recurring role in Emergency Ward 10 and had unsuccessfully auditioned for the part of Ben Jackson earlier in 1966. He had also worked with Patrick Troughton on Smuggler's Bay in 1964.
A popular myth states that Jamie was kept on as a companion due to positive audience reaction. This is untrue. Frazer Hines actually completed location filming for following story the Underwater Menace three days before the first episode of the Highlanders was transmitted. A scene where he didn't join the TARDIS crew was filmed, however.
Jamie is the longest serving companion in the TV series, clocking in 113 episodes during his original run, plus appearances in The Five Doctors and The Two Doctors during the 1980s.
Hannah Gordon, who played Kirsty, returned to Doctor Who 37 years later to voice Skagra's ship in the BBCi webcast of Shada.
As far as we can tell, The Highlanders is the first example of the Doctor cross-dressing, as he disguises himself as a washer woman. He was a cleaning lady in The Green Death some years later.
Although all four episodes are missing from the BBC archives, three clips from part one (grand total|: about 13 seconds) exist on 16mm film. These were all sequences cut from the episode by Australian censors and unearthed in 1996 by Damian Shanahan. The scenes feature Alexander killing a Redcoat and the Doctor, Jamie, Ben and Colin about to be hanged.