The episodes feature William Hartnell in the lead role
A cardboard box found in a collector's "ramshackle" collection of vintage films contained two episodes of Doctor Who that have not been viewed since airing in the 1960s.
The episodes feature the first incarnation of the Doctor, played by William Hartnell, tackling a Dalek plan to take over Earth, the solar system and the galaxy in a storyline only ever shown in the UK.
Peter Purves, who played the Doctor's assistant Steven Taylor, was invited to the Phoenix Cinema in Leicester on Wednesday under false pretences to view the two episodes, and he said: "My flabber has never been so gasted."
Restored versions of the episodes will be released on BBC iPlayer this Easter.
The first episode, titled The Nightmare Begins, was part of the third season of Doctor Who and was aired in November 1965.
The second recovered episode, Devil's Planet, was broadcast two weeks later.
William Hartnell appeared as the first incarnation of the Doctor alongside assistant Steven Taylor, played by Peter Purves
The intervening episode, Day of Armageddon, was found in 2004 by a former BBC engineer, meaning fans now have the first three instalments of The Daleks' Master Plan arc.
Written by the creator of the Daleks, Terry Nation, and Dennis Spooner, the serial starred Hartnell and Purves alongside an early appearance by Nicholas Courtney as Bret Vyon, Adrienne Hill as Katarina, and Kevin Stoney as Mavic Chen.
Courtney would go on to play recurring character, The Brigadier.
But the "dark and gritty" 12-part storyline was ordered to be wiped, and more than half of it remains missing.
Reels were found in a cardboard box as part of an "eclectic" collection of thousands of films
So how did they become the first lost Doctor Who episodes to be announced to the world since 2013?
The work of Leicester charitable trust Film is Fabulous! (FIF) is behind what had become the longest gap between lost episodes being uncovered coming to an end.
Many previous lost episodes had been found in archives of TV stations overseas, including the last episodes found, which had been recovered from a Nigerian TV station.
But with The Daleks' Master Plan, the story was not sold overseas.
Two episodes of The Daleks' Master Plan from 1965 have been discovered among an amateur collector's estate
Censors in Australia and New Zealand deemed it too violent, and without their buy-in, selling to other markets was not profitable.
Combined with the move towards colour, the black and white story was thought to have little future value and consigned to the bin.
But copies of some episodes were still made by technicians to check for problems which might need to be fixed ahead of pitching the episodes to other markets.
It was these versions that made their way to an amateur collection.
Professor of cinema and television history at Leicester's De Montfort University, Justin Smith - chair of trustees at FIF - said "a debt of gratitude" was owed to the anonymous late collector, whose films - largely focused on his love of trains and canals, including hundreds of home videos - were donated to FIF after he died.
Prof Justin Smith said the finds were "gems"
He said: "We travel all over the country to recover film collections from private hands.
"A lot of the films had suffered water damage and the cans had corroded.
"These are gems in what was an eclectic and ramshackle collection, a lot of which hadn't been looked after as well as the Doctor Who had.
"The collector did recognise what he had, but how he acquired them has been lost to time."
News of the discovery left actor Purves, 87, tearing up after travelling to Leicester on Wednesday to attend what he believed were going to be interviews with the media about television in the 1960s.
Learning the real reason he had been lured to the venue with "a perfect lie", he said: "I'm speechless, knocked out."
Peter Purves was emotional when he was told the real reason for his trip to the East Midlands
And after viewing the two episodes, he said, "my flabber has never been so gasted", although he quipped: "I've never forgiven the BBC for losing those episodes, it would be really nice to get a few royalties."
Purves added: "I'm not sure I even saw those programmes go out originally - I remember the stories, but having seen them, the pictures are unfamiliar to me.
"I didn't remember the first one when I was still almost comatose following the injury I received fighting in Troy in the wonderful Mythmakers - which of course is missing."
Six decades after being broadcast, the two episodes were played on the big screen this week
Recalling the industry in the pioneering days of TV sci-fi, Purves said: "It was just a job. It sounds silly but we did an episode of the programme each week, in the year I did 46 episodes.
"It was great fun and was great to be doing a series that was hugely popular.
"But it was a difficult time, I won't pretend it was easy, the cast kept changing and it seemed a bit of a time of flux.
"In the two episodes we've seen there was a great performance by Nick Courtney playing Bret Vyon.
"I was concerned very much that he was there as a replacement for me.
"As it happens, he got killed in episode four or five."
Hartnell puts in a memorable performance in the episodes, which make up some of the first in the storyline
Purves expects the lost episodes being rediscovered will reignite interest in the early seasons of the show.
"It was the fourth appearance of the Daleks and it'll be exciting to fans for a lot of reasons," he said. "The fans of Doctor Who are legion, and they seriously love the classic times.
"I'm astonished these two wonderful episodes have finally turned up - so many of my episodes are missing - it's heartbreaking to me.
"I'm absolutely thrilled and maybe I'll [get] quite a few invites to conventions and various things."
Doctor Who historian Toby Hadoke, who "lured" Purves to Leicester for the event, expects the Doctor Who fanbase will be "thrilled" by the news of the episodes surviving through the decades.
Toby Hadoke says he dreams of finding lost episodes of Doctor Who in places like car boot sales
He said: "It was really touching, and what a privilege.
"We never thought we'd see these episodes again. It was a real factory process, no time for post-production or anything like that, never repeated, never sold abroad.
"People will be thrilled. The thing about Doctor Who is it's a connection to your childhood.
"I'm a grown man and I've been wishing I could see The Nightmare Begins since I saw the name on a list of missing episodes of Doctor Who 30 years ago.
"Forget Glastonbury, I think if you put on a screening of these tomorrow it would sell out in seconds.
"They really are the holy grail."
A special screening of the two episodes organised by FIF, with Purves as guest of honour, is being held in London on 4 April.
Details of the event are yet to be announced, but it will take place on the same day the two restored episodes are made available in full on BBC iPlayer.
Episode one sees the Tardis landing on the planet Kembel in search of help for the Doctor's injured companion, only to learn the Daleks are planning with Guardian of the Solar System Mavic Chen to conquer the Earth.
By episode three, the Doctor has stolen a vital component needed for the conquest, but after leaving Kembel they are forced to land on penal planet Desperus - pursued by the Daleks.
Noreen Adams, director of BBC Archives, said she was "thrilled" the episodes would be released on BBC iPlayer.
She said: "BBC Archives has been working to restore the original recordings and update these to broadcast quality, ensuring fans can enjoy a little extra treat with their Easter Eggs this April."
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