The fourth episode of The Dominators was shown today in 1968. It was the penultimate instalment of the story - though that hadn't been the plan originally. The six part version was reduced to five by script editor Derrick Sherwin, much to the annoyance of the writers.
Today we remember a pair of key figures - one behind the scenes and one on screen.
The latter actor is Michael Sheard, who appeared in the series on six occasions. He died today in 2005, aged 67.
His first role was as medic Rhos in The Ark in 1966. He skipped the Troughton era and was next seen as another doctor - Summers, in The Mind of Evil during Pertwee's tenure.
The third appearance is the one he's best remembered for - the doomed Laurence Scarman in Pyramids of Mars. A second Tom Baker role was as Supervisor Lowe of Titan Base in The Invisible Enemy.
In Peter Davison's first story he was a medic again - Castrovalva's apothecary Mergrave.
His last role was as the Headmaster of Coal Hill School in Remembrance of the Daleks. (The latter also featured George Sewell, whose birthday it would have been today. He died in 2007 aged 82).
Outside of Doctor Who he was associated with another famous fictional school - Grange Hill - in which he played the horrible Mr Bronson.
He had some notable big screen roles, including Imperial Admiral Ozzel in The Empire Strikes Back, and Adolf Hitler in Indiana Jones and the Last Crusade. Hitler was a role he played on four other occasions (including The Tomorrow People), and he also played Himmler three times.
Behind the scenes, we remember Gerry Davis, the series' fourth script editor, who died today in 1991, aged 61.
During his tenure he introduced the popular base-under-siege scenario and played a major role in developing the character of the Second Doctor, having overseen the series' first change of lead actor. He introduced a scientific adviser to the programme - Kit Pedler - with whom he created the Cybermen, and also later devised the Doomwatch series.
He left the series part way through Evil of the Daleks and later moved to the USA to work. He novelised some Cyberman stories for Target, but is last TV story - Revenge of the Cybermen - was heavily rewritten by his later successor Robert Holmes. (His first job on Doctor Who had been to rewrite his predecessor's work on The Celestial Toymaker, so he couldn't really complain).
He tried to tempt the JNT production team with a Cyberman origins story but this wasn't taken up.
After the series had been taken off the air, he and Terry Nation formed a partnership to produce the series independently, but this offer was declined by the BBC.