When Sue Malden started working as an assistant researcher for the British Broadcasting Corporation (BBC) in the early 1970s, she imagined the broadcaster’s 20-plus year history of television was tucked away somewhere on shelves—a towering video library of cultural history from the Queen’s 1953 coronation to hundreds of episodes of Doctor Who.

But as Malden began to familiarize herself with the spare inventory of past programming, the reality was much different. “What I found was that there were many gaps,” Malden tells Mental Floss. “A lot of things just weren’t there.”

It would take years, but when Malden eventually assumed the post of Television Archive Selector in 1979, she had educated herself on the BBC’s stern and unsentimental methods for dealing with the bulk of their content. Because shows weren’t often repeated, there was no long-term need to retain them. And because videotape was an expensive storage medium at the time, it was far more sensible to reuse cassettes rather than buy new ones.

The company kept a bulk-erasure machine on hand to systematically wipe out shows that were believed to have exhausted their usefulness. Reams of paperwork indicated a large chunk of their content was rubber-stamped into destruction using just three words: “no further interest.”

As Malden tried to corral the wastefulness, she decided to use Doctor Who as a research guide to track the steps of how the BBC went from filming a series to ordering its demise.

Out of 253 produced episodes of Doctor Who, the BBC had not a single original copy left.

For much of the 1950s, television in the UK was viewed in much the same way as the radio programming it was beginning to replace: Live newscasts, teleplays, and other series were intended to be consumed in the moment. If viewers really liked something, then it would be “repeated” by reassembling the actors and performing it for a second time.

“Television meant being live, over, and done with,” says Richard Molesworth, a BBC historian and author of Wiped!, a detailed chronicle of how the channel discarded a large chunk of Doctor Who history. “When videotape came about in the late 1950s, it wasn’t seen as a means of preservation or as an archival format," he tells Mental Floss. "It was in case a program was to be repeated in a short period of time—days or weeks.”

The two-inch tape adopted by the broadcaster beginning in 1958 was perceived as a way of getting a program on the air by having completed and edited footage ready for transmission. Across departments, there was virtually no incentive to treat those tapes as part of a long-term storage approach. In fact, it was the opposite: Because tapes often came out of a show’s budget, wiping old episodes and reusing them saved money. Barely any episodes from the entire first season of The Avengers, for example, are believed to have survived; Z Cars, a popular cop drama, was also snuffed out.

The lone motivation for not disposing of content immediately was the potential for overseas sales, a lucrative enterprise that allowed the BBC to capitalize on its inventory in foreign markets. But once BBC Enterprises—the arm responsible for dealing with those markets—struck a 16mm print of a taped show (which guaranteed compatibility, as video formats differed) and sent the film to the buyer, there was no reason to retain the tape. By the time BBC 2 debuted in 1964, virtually doubling the amount of content being produced, the order to “wipe” shows by deleting them in the bulk-erasure unit reached an all-time high. Unlike the U.S., with its many fractured local affiliates, there weren’t multiple copies of shows to ensure their continued survival. If the BBC scrapped it, it was likely scrapped for good.

Producers, Molesworth says, tried to resist the extinguishing of their media. Dudley Moore and Peter Cook tried to pay out of pocket to make certain their series, Not Only... But Also, remained in existence. They were turned down. (Monty Python experienced a similar incident, fearing they’d be wiped, but Monty Python's Flying Circus was too pervasive in America for that to have happened.)

When tapes would begin to pile up in dressing rooms, corridors, and other areas, it became an untenable situation. “New productions would need tape, and no one would want to spend money on new tape,” Molesworth says. “Not when there was perfectly good tape sitting right there.”

When the BBC began issuing color television licenses to viewers in 1969—a fee that essentially amounted to a donation for programming—the problem grew malignant. There was now even less incentive to keep black-and-white programming for either local consumption or to sell abroad. And when series were sold off, buyers typically had to adhere to the BBC’s “burn or return” policy. If the film wasn’t returned after the contracted number of airings, it was to be incinerated, with a “certificate of destruction” returned to the UK.

While the practice would later be vilified as a kind of cultural vandalism, there was no malice on the part of employees. For most of the programming, talent contracts prohibited more than one or two airings; relying on public funds for support meant tight budgets. No one really considered the programs could have a life decades into the future. “Had they kept those tapes, and newspapers found out they were sitting on hundreds or thousands of hours of programs they couldn’t show, they’d be accused of wasting public money,” Dick Fiddy, a consultant to the British Film Institute (BFI), tells Mental Floss. “What they did was good housekeeping.”

By Molesworth’s estimate, 60 to 70 percent of all BBC programming produced between the mid-1950s and mid-1970s was deleted. It was an amazing number of casualties, but the bleeding would soon halt thanks to several factors.

Around 1975, control of managing tapes went from the Engineering Department to the BBC Film Library, which was soon renamed the BBC Film and Television Library. There, archivists were not motivated by budget to keep programs shelved. At the same time, newspaper articles began to point out that the BBC had been rather mercenary in their approach to archival material. As the VHS revolution was just starting and people with home recording units were able to preserve programming, they found it unsatisfactory that the broadcaster itself wasn’t retaining content.

Financially, the latter was beginning to make a lot more sense. Exports like Monty Python’s Flying Circus, sold to American public television affiliates, were becoming profitable, and actor’s equity had eased demands on payments for repeats. That, coupled with the lowered cost of storage and the increased revenue from selling color TV licenses to viewers, led to a paradigm shift. According to Malden, however, it took some time to convince employees.

“I remember going around to heads of production departments and explaining what we wanted to do, which was keep everything,” Malden says. “And sometimes I’d hear, ‘Well, OK, but this episode wasn’t a writer’s or actor’s best work.’ I’d have to say, ‘No, look, it’s all the output.'" The engineering department, once tasked with exploiting every inch of tape it could, looked at Malden’s approach with puzzlement. “They basically asked, ‘Why on Earth do you want to keep all of this?’”

Once Malden felt confident the current crop of programming wasn’t going to be obliterated, she began looking to see if the gaps in the archive could somehow be restored. “A lot of programming went out live in the 1950s and 1960s, so there was never any recording to lose,” she says. “It was better to look at an iconic series, see how many were broadcast, see how many exist, and what happened to the rest.”

Doctor Who was an easy choice. Debuting in 1963, the low-budget series about a time-traveling alien who could regenerate to explain his repeated recasting had become a cultural institution that was still on the air. (And would remain so until 1989, at which point it took a 16-year break before resuming in its current incarnation.) Malden found just 57 episodes out of the 253 produced through that time scattered throughout the BBC's various departments. Some had even been earmarked for destruction when Malden was still in the process of staying their executions.

To try and restore the BBC’s past, Malden and other historians had a remarkable resource: the foreign territories where the BBC had sold off several programs. Some didn’t bother either returning or destroying the 16mm film reels they had been supplied with. In writing to these stations, Malden discovered episodes of Doctor Who and other material that had survived the intervening years as a discarded and forgotten canister in a storage room. In other instances, various BBC departments had retained Doctor Who episodes after they had been returned by buyers. By 1981, Malden wound up securing 116 of the 253 episodes.

The BBC, however, had no official staff devoted to repossessing content. That fell in some measure to Malden, who effectively managed to assemble a small group of volunteers when a 1981 magazine article publicized the large chunk of missing Doctor Who episodes. “I started getting lots of letters from fans, saying ‘There might be a copy here,’” she says. “That gave me a lot of leads to work with.”

At the same time, a Who fan named Ian Levine had approached the BBC looking to buy original copies of episodes for his own private collection. He was introduced to Malden, and together they found a number of crucial episodes throughout the 1980s.

In 1983, a Mormon Church in London was cleaning out its basement when several BBC film cans, including two episodes of Doctor Who, were discovered among the clutter. In 1985, Levine found several episodes idling in a Nigerian television station. Two more episodes were returned to the BBC after being found at a yard sale. On a few occasions, Malden was able to retrieve episodes that had been seized by BBC employees simply because they were fans of the show.

Eventually, the idea of writing or faxing foreign TV stations to find episodes slowed to diminishing returns. (An Iranian station, asked to look for content, responded with incredulity. According to Wiped!, they wrote back asking, “In the name of Allah, what are you talking about?”) That paved the way for television archaeologists to try to physically locate missing prints.

A company called Kaleidoscope worked with both the BBC and the BFI to scout yard sales and private collections for material. In 2011, a footage hunter named Philip Morris located nine missing episodes of Doctor Who in Jos, Nigeria, where employees had ignored instructions to burn them. His company, Television International Enterprises Archives, seeks to “repatriate” old British television from foreign sources.

Although fans of Doctor Who have virtually guaranteed that the most zealous searches will be reserved for the remaining 97 episodes of the series that are still missing, the BBC doesn’t play favorites when it comes to accepting lost programs. Dozens of old television plays, including one titled Colombe featuring Sean Connery, were recovered from the Library of Congress in 2011 because they had been acquired for public broadcast in the States; Fiddy organizes a semiannual event called "Missing Believed Wiped," which celebrates recovered material of every stripe. Recent screenings have included a film directed by a young Ridley Scott, a previously thought-to-be-lost episode from the first season of The Avengers, and footage of Woody Allen boxing a kangaroo. A 1967 show titled At Last the 1948 Show featuring Graham Chapman and John Cleese was discovered in 2013 and is considered a precursor to Monty Python; it went unseen for nearly 50 years. Fiddy located them from a producer who had filmed the television screen with a 16mm camera.

“It’s sort of a return to the way television used to be viewed,” Fiddy says of his media festival. “The only thing that links the material together is that it’s been rediscovered. People will stay and watch things they wouldn’t otherwise.”

How much more undiscovered material is out there is open to debate. Malden and Molesworth believe that overseas stations have probably been exhausted for material, and enough press has been devoted to the search for Doctor Who episodes over the decades that any private collectors have likely already come forward. But Morris thinks there’s more to be unearthed in the Middle East and Africa; Fiddy continues to have enough material for his screenings, with bits and pieces of the BBC’s history rematerializing all the time.

“We want to find things for cultural value, for what it tells us about the past,” he says. “The more witnesses you’ve got, the more accurate you can be.” Fiddy’s holy grail of sorts remains Madhouse on Castle Street, a 1963 film starring Bob Dylan.

Today, it’s inconceivable HBO would scrap a Game of Thrones episode after two airings. But 50 years ago, television was simply a diversion that wasn’t supposed to endure. “Television is such an important part of reflecting our society,” Malden says. “I don’t think we should ever give up looking.”

Additional Sources: Wiped! Doctor Who’s Missing Episodes