31 January 1970
Nicholas Courtney (Brigadier Lethbridge-Stewart), Fulton Mackay (Dr. Quinn) [1-3], Norman Jones (Major Baker) [1-5], Peter Miles (Dr. Lawrence) [1-6], Thomasine Heiner (Miss Dawson) [1-5], Ian Cunningham (Dr. Merh) , Roy Branigan (Roberts) , John Newman (Spencer) , Bill Mathews (Davis) , Paul Darrow (Captain Hawkins) [2-7], Nancie Jackson (Doris Squire) , Gordon Richardson (Squire) , Pat Gorman [2-4], Paul Barton [4-5, 7], Simon Cain [4-7], John Churchill [4-5, 7], Dave Carter  (Silurians), Peter Halliday (Silurian Voices) [2, 4-7], Geoffrey Palmer (Masters) [4-6], Richard Steele (Sergeant Hart) [4, 6], Ian Talbot (Travis) , Dave Carter (Old Silurian) [4-5], Nigel Johns (Young Silurian) [4-7], Harry Swift (Private Robins) , Pat Gorman (Silurian Scientist) [5-7], Alan Mason (Corporal Nutting) [6-7], Derek Politt (Private Wright) , Brendan Barry (Hospital Doctor) .
|Written by||Malcolm Hulke|
|Directed by||Timothy Combe|
|Produced by||Barry Letts|
While caving in Derbyshire, two pot-holers are attacked by a huge creature and one is killed. at the nearby Wenley Moor nuclear research centre, which is built into the same caves, there are strange power losses threatening the reactor. Not only is everyone is at a loss to explain these incidents but there is also a high number of breakdowns involving staff members.
Now exiled to Earth and working for UNIT, The Doctor and his assistant Liz are sent for. As the surviving pot-holer begins to make cave-paintings in his ward The Doctor discovers not only a Tyrannosaurus Rex but a colony of Silurians – intelligent, walking lizards who have been dormant formillions of years. Now they have awoken to find that mankind has replaced them as the rulers of Earth – and they want it back. Can The Doctor find a way of thwarting their plans or will humanity be wiped out to usher in a new Age of the Lizards.
- The Silurians reappear in Warriors of the Deep, Bloodtide, Blood Heat and The Hungry Earth/Cold Blood.
- In an alternate timeline created by the Meddling Monk (The Time Meddler), these events ended with the death of the Third Doctor at the hands of Silurian Morka, beginning a decline of Earth until the Seventh Doctor arrives in Blood Heat.
- Blood Heat and Final Genesis both take place in (separate) alternate timelines which diverge from this story. In both versions, the Third Doctor dies, with completely different outcomes for Earth’s history.
- Sea Devils, the Silurian’s”aquatic cousins”, appear in The Sea Devils.
- The journalist to whom the Brigadier briefly speaks over the phone at the Wenley Moor nuclear research facility is James Stevens of the Daily Chronicle, who received the number from a mysterious contact. (Who Killed Kennedy)
- The failure of the Wenley Moor nuclear research facility, among other incidents, was publicised by Stevens in his “Bad Science” series of articles, Harold Wilson’s position as Prime Minister of the United Kingdom became untenable and the Labour Party lost the general election in June 1970 to the Conservatives, led by Edward Heath. (Who Killed Kennedy)
- Several weeks after the plague outbreak, Doris Squire was still being treated for shock”after claiming to see some sort of lizard walking upright like a man”. According to Stevens, this story did not even make the gutter press. (Who Killed Kennedy)
- Under the pseudonym”Victor Magister”, The Master was charged with having caused the plague outbreak, among other incidents, after being captured in Devil’s End. Stevens notes that his terrorist activities were little remembered by most British people in 1996. (Who Killed Kennedy)
- By the time of his second incarnation, The Doctor had heard tales of a sentient race which evolved on Earth before humanity but had not yet encountered them at that point in his personal timeline. (The Wheel of Ice)
- Dr. Lawrence and Masters received letters which predicted the exact dates and times of their deaths from the Apocalypse Clock. Lawrence died at 4pm on 21 November. (The Last Post)
- In a parallel universe in which The Doctor’s exile on Earth did not begin until 1997, this crisis was resolved by Captain Mike Yates and his men travelling back in time millions of years to destroy the Silurian civilisation using fourteen nuclear warheads to prevent their eventual reawakening in the 1970s. This resulted in the creation of a crater in the middle of London. (Sympathy for the Devil)