Deep inside a giant shed in a business park in west London, Dean Cripps is preparing to digitise some old film. It came up in a canister from one of the vaults downstairs, at the BBC Archive Centre in Perivale. A second reel carries the magnetic track, or sound. Cripps, who is 61 and has worked in the archive for 43 years, feeds the reels through an old telecine machine, lining up the sync marks at the start of each film. Soon the machine is whirring away, spooling through another piece of broadcasting history. Cripps controls the speed with a mechanical lever, watching images flicker across the screen in front of him. He looks as if he’s driving an old tube train. The film is an episode of The Camera & the Song, a music show that aired on BBC Two in the early 1970s. A crackly, familiar voice fills the room – a rarely seen early performance by Victoria Wood, who made it into an episode of the show in 1976, aged 22. She plays piano while singing about a young woman in suburbia: “Children be nice to your father / He is still alive at 35 / While your eyes get brighter / His trousers get tighter.” The machine scans the film as it is played, so that it can be converted into a digital video file. Metadata will be added, including the programme’s original Radio Times listing. A powerful speech-to-text system introduced by the BBC in 2015 will then create a searchable transcript of the episode, adding that to the file, too. The film canisters will be sent back down to the vaults, where they are stored at low temperatures that require the archivists working on them to wear fleeces. The new digital version of a young Victoria Wood will go up to the cloud. It will join a digital archive that is becoming so vast and accessible that it is beginning to operate as a kind of parallel internet – a constantly growing chronicle of a century that technology is only now opening up. A Dalek stands guard in the entrance to the building, which opened next to a bus depot in 2010. Further inside, more than 12m tapes, vinyl records, CDs and other redundant formats sit on 60 miles of shelving in nine climate-controlled vaults. The building is the biggest facility run by BBC Archive, which employs more than 200 people. All the big moments are here, including the Queen’s coronation – and, a few weeks after my visit – her funeral. There are moon landings, encounters with gorillas, Live Aid, the EastEnders theme on an infinite loop, and Del Boy falling through a bar. In one dimly lit booth, Deepak Mahil is doing a quality control check on an episode of EastEnders from 1993, featuring two smooth-faced Mitchell brothers. After digitisation, files are screened for “ingest faults”, or glitches. In another office, technicians are digitising more than 200,000 CDs used for archiving radio in the late 1990s. In some cases, the sticky labels applied to discs had corroded the data layer. “We’d open them and just get silvery dust falling out,” says Nick Ashcroft, as he shows me a ruined recording of Radio 3’s Private Passions. “Luckily we had a backup.” Trolleys carry reels for processing, their modern cataloguing barcodes stuck next to old labels in a palimpsest of yellowing paper and tape. I spot a broadcast of Nureyev’s Nutcracker from 1968 and, from 1957, a recording of Cy Grant, the first regular Black performer on the BBC, who shared “topical calypso songs” on Tonight with Cliff Michelmore, the One Show of its day. In the sound vault, I see tapes of David Bowie performing Space Oddity on Johnnie Walker’s Radio 1 Lunchtime Show. The BBC’s attitude towards preserving and using its broadcasts has transformed in the 100 years since it was formed in October 1922. The technology didn’t exist to record the earliest programmes, which were all broadcast live. When recording television became possible, starting in 1947 with a variety show at Alexandra Palace, the cost of tape made keeping programmes too expensive. Most tapes were overwritten and eventually binned. Where it happened, archiving could be haphazard. Some recordings were kept only long enough for repeats to be aired in the days when film reels were used to play out recorded programmes. Cripps remembers playing Christmas films this way in the early 80s. “Each film was probably 12 cans and you’d have them going out on a machine like this, a bit like a cinema,” he says. Much has been lost, including hundreds of episodes of Hancock’s Half Hour, Dad’s Army and Doctor Who. Archivists and fans of shows have long tried to fill the gaps, sometimes unearthing programmes on used tapes that had been sold to foreign studios for overwriting. Last year, the BBC screened a long-lost episode of The Morecambe and Wise Show that Eric Morecambe’s son had dug out of an attic. As the cost of archiving came down with new technology in the 1970s, the BBC also came to realise the value of preserving more. In 1981, the corporation added to its charter a requirement to keep everything. Digital archiving began with all radio in 2007, and all TV from 2015. Today, thousands of hours of TV and radio are constantly – and automatically – uploaded and preserved. The whole digital archive, which includes more than 85% of the 550,000 unique programmes stored at Perivale, now amounts to more than 23 petabytes, the equivalent of almost 100 years of high-definition video. I sit down with Helen Toland and Claire Coss, who are both 47. Toland, a former BBC radio producer, is now an editor at the archive based in Belfast. Coss, the head of product at Perivale, joined the archive in 2000 as a graduate researcher. “I was a complete telly addict so it was a dream job,” she says. Toland opens her laptop and logs on to Archive Search, the BBC’s internal search engine. The corporation is still discovering the power of this portal, which contains almost 40m recordings spanning much of the past century. “There has been this big change in our mindset in recent years,” says Toland, who joined the BBC in 2002. “We’ve stopped thinking of this as just an archive but as this amazing pool of on-demand content to be discovered and shared.” Digital storage solves several problems, including the otherwise inexorable demand for shelf space and big sheds. Soon after my visit, the BBC learns that the lease on the Perivale site won’t be renewed, forcing it to find a new facility by the end of next year. In the cloud, recordings won’t degrade, or become unplayable as old machines become obsolete. The new search engine is a boon for programme makers, who no longer need to request physical media from the vaults. Adam Curtis, perhaps the most famous miner of the archives, uses it for his documentaries. News producers have direct access. The recent deaths of Mikhail Gorbachev and the Queen created a lot of demand for archive material, although, as with newspaper obituaries, much is prepared in advance. During the first pandemic lockdown, one producer used Archive Search to make a 40th-anniversary film about Children in Need from her parents’ house on her laptop. “She wouldn’t have been able to do that even a couple of years earlier,” Coss says. But the real value in the digitisation process has been the capacity to mine the archive for treasures that had become lost within it. Major recent advances in automated transcription technology have been vital. Machine learning – the practice of teaching computers to make improvements by themselves – is helping the speech-to-text system identify speakers and cope with accents and obscure words. Until recently, you couldn’t search the archive for much more than programme names. Now it can be searched for anything. Not long ago, someone had asked the archive what it had on the Grateful Dead, the US psychedelic rock band that formed in 1965. Toland repeats the search on her laptop. More than 800 results include The Old Grey Whistle Test. The oldest entry is an episode of Panorama, broadcast in 1966, that explores the burgeoning tech industry in what would later be known as Silicon Valley. There is no mention of the Grateful Dead in the brief description that had been stored with the original film. But when Toland clicks on the transcript that was added during digitisation, the words “grateful dead” are highlighted at 37 minutes. With another click, Toland skips to a segment filmed in one of “the psychedelic dancehalls” of San Francisco. And there, singing to tripping young Americans, is a 23-year-old Jerry Garcia. These few seconds of film, for decades hidden within a tech documentary, capture the birth of a major rock band – and the hippy movement itself. Toland, who has the zeal of an Egyptologist, shows me another example. One of her colleagues was searching recently for content about the Marshall plan, the US’s postwar economic rescue package for western Europe. This time, the oldest result, broadcast in 1948, is just called “newsreel”. There is no other information. The film begins with silent footage of a football match, soon cutting to some ships being launched. “And then, all of a sudden, that stuff ends,” Toland says, scrolling through the film’s transcript tab. After the football and the ships, the film cuts to what Toland thinks was its first recording, before it was overwritten. It’s the swearing in of General Omar Bradley as chief of staff of the US army. At a press conference, the outgoing chief, the future President Eisenhower, discusses the impact of war on Europe, and recalls watching a German field marshal sign the instrument of unconditional surrender in 1945. “We think this is a piece of footage that no one else has seen,” says Toland, who checked the Eisenhower Presidential Library. “And there will be loads more like that, because of the availability of the transcriptions. We can find content that is here but was never catalogued.” I had first wondered what was going on in the archives when, a couple of years ago, I began to notice random clips going viral on social media. Toland says her department realised the popular potential in its blossoming archive in 2016, when it posted to its Facebook and Twitter accounts a clip from a 1971 episode of Nationwide about clackers. The faddish toy, made up of hard plastic balls on a string, had been injuring children. “It got about 20m views in the days when that was just unbelievable,” says Toland, who thinks nostalgia inspired people to share the clip. Today, a team of producers runs the archive’s social media accounts, which have 2.1 million followers on Facebook alone, mining Archive Search for clips that may strike a chord. Sometimes it’s obvious what to look for. There has been a lot of Queen content lately, for example. But the team also watches whole episodes of shows known to contain rich seams, including That’s Life and Whicker’s World. Tomorrow’s World does very well; a 1979 item about advances in “home-working technology” felt relevant in 2022. In 2016, archivists spotted a familiar face while reviewing a 1995 episode of Good Morning with Anne and Nick. A teenage boy called James Corden had won a competition to do a turn as a presenter. He interviews Meat Loaf, who encourages him to never give up on his dreams. It would be Corden’s first onscreen appearance, 20 years before he resumed celebrity interviewing in the US. The clip went viral last January when the archive reposted it after Meat Loaf’s death. “Of course, Corden went and shared it himself and didn’t credit the BBC,” Toland says, laughing. Other viral hits have included a That’s Life item from 1988 in which Nicholas Winton, the stockbroker who brought Jewish children to the UK from Nazi Germany, sobs when Esther Rantzen reveals that all the people sitting around him in the studio audience are former refugees who owe him their lives. Ordinary, often unnamed people can get the biggest audiences. In the week of my visit to Perivale, the archive accounts have posted a clip from a 1961 episode of Whicker’s World, in which Australians reveal what they expect to find as they prepare to emigrate to England. One fabulously supercilious young woman says English women are “very suety … Dumpy women, plump – uninteresting.” The clip got 2m views in a couple of days. As the archive’s digitisation work came to a head in the run-up to the BBC’s centenary, Toland and her team launched a new public portal to some of its news and current affairs output. BBC Rewind, which went live in July, so far includes more than 30,000 clips that are categorised and tagged as pins on a map. In my own area in south-east London, I find South of the River, a fascinating 1964 documentary about social change, as well as a Newsround report from 1973 about a police pursuit of an escaped eagle on Bird in Bush Road, Peckham. Toland’s team welcomes people to get in touch if they see familiar faces on Rewind or its social media posts. The archive also works with regional BBC news shows to tell stories of such discoveries. BBC Look North recently interviewed a woman who was moved to tears after watching a 1979 report about her late mother, a former train driver, years after her death. “We have had so many people get in touch with stories like that,” Toland says. Toland knows the feeling. Soon after she started work at the archive, she remembered wangling a ticket to see REM on Later … with Jools Holland in 1998. She was 24 and a huge fan of the band. She found the episode on Archive Search, which contains more than the BBC is able to share publicly because so much remains protected by copyright, and spotted herself in the front row. “As you get older, you don’t have the same opportunities to indulge your passions, but watching it just reminded me how much I love music,” she says. People who find themselves in the archive, or think they might appear in it, can now request a digital file for a £60 fee. I decide this might not be worth it when I find myself. In 2013, with slightly more hair, I had been interviewed on BBC Breakfast the morning after a theatre ceiling had collapsed during a play I was watching. The growth and searchability of the digital archive has commercial value, expanding what the BBC is able to sell to outside film-makers and other clients. As the Eisenhower clip shows, the archive’s value to historians is clear, and the BBC makes all of it available to schools and universities. But Toland and Coss think the material now being unlocked in the vaults has even greater potential. “We’ve always known the archive is a treasure,” Toland says. “But we’ve realised only recently that it’s also a massive pool of data about the human condition.” The archive charts changes in accents, fashion, diets and social mores, as well as attitudes to the great issues of the past century, from war to climate change. “It really is the cultural and social memory of the UK,” Coss says. Toland wants academics to begin to imagine how it might be mined for more than viral clips. “Fifty years ago, people would never have dreamed that we would use the internet in the way that we do today,” Toland adds, closing her laptop. “I think in another 50 years, we will be using this archive in ways we can’t imagine. We’re only scratching the surface.”