On Saturday March 26th 2005, a quiet revolution was happening in people’s living rooms. Across the nation a long-cancelled sci-fi TV series - an oft-mocked, dismissed relic - was fighting its way back into the cultural conversation in one short 45-minute adventure.

Doctor Who had regenerated – even if the character didn’t actually do so onscreen – because on that day, 15 years ago, BBC One aired Rose for the first time. And that was just the beginning.

Looking back a decade-and-a-half later, it’s easy to forget what a risk that episode was. The Doctor in a leather jacket, accompanied by a popstar-turned-actor and fighting off evil shop window dummies? How would that satisfy anybody, fan or newcomer?

Of course today we know that Rose (penned by then-showrunner Russell T Davies) introduced a whole new generation to Doctor Who, reshaped the pop culture conversation around itself and became the first step in a journey that continues to this day as work continues on new episodes, 12 series later.

But at the time, no-one really knew whether Doctor Who would work in the new millennium – not even the people making it.

"We didn't know whether Doctor Who was going to last for more than a year," Nicholas Briggs, regular voice of the Daleks since 2005 (and voice of the Nestene Consciousness in Rose) recently told RadioTimes.com.

"You never know what something's going to look like when it's finished, or what's going to be happening in the world when it's released. Sometimes really brilliant things are scuppered by some huge news story, just like Doctor Who almost was in the first place [in November 1963] with the assassination of President Kennedy."

Luckily, this time Doctor Who dodged any major obstacles to bring Rose to screen with minimal hiccups (though the episode was leaked online, which Sydney Newman and Verity Lambert didn’t have to worry about), the reaction was hugely positive and the rest, as they say, is history.

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And revisiting the episode in 2020, it’s not hard to see why Rose was such a hit. Christopher Eccleston and Billie Piper are spot-on from the get go, the gags work well and the episode never pauses breath long enough for the cracks to show even if there were any.

While we’re used to it now, at the time foregrounding the companion (Piper’s titular Rose Tyler) was a brilliant twist on the Doctor Who format, essentially making the Doctor (Eccleston) a supporting player in his own series.

In a heightened world of monsters, time machines and living plastic Rose felt real, from her overbearing mother Jackie (Camille Coduri) and slightly useless but not unrealistically awful boyfriend Mickey (Noel Clarke) to her flat, her clothes, her job – everything. The high-flying sci-fi was all the easier to accept because it felt like it was happening to us, in our world. And that’s only a small part of what Rose (the episode) was doing.

As Russell T Davies wrote in his script book for the 2005 series, "It had to convince everyone – and I mean everyone within the BBC, long before the viewing public got involved – that their faith hadn’t been misplaced; that an old, tired, niche, cult sci-fi show could work in the mainstream once again."

Considering how many Doctor Who episodes would later go on to be extended to an hour or longer, it’s frankly astonishing how much Rose gets done in 45 minutes. While today we might need a whole episode just to properly meet a new companion, here we get to know Rose, meet a new Doctor, learn the basics of the show, solve a mystery, defeat the Autons and tee up the series’ future adventures at a breakneck pace. And it never feels rushed, or like we’re not spending enough time on anything – the pace is perfect.

"Every scene, every beat, every character had to operate as a signal, telling everyone – accountants, designers, writers, management – what we wanted. Defining what Doctor Who is to be," Davies wrote.

"Monsters? There’s the Nestene. The everyday world? Hello, Jackie. Mystery? That’s the Doctor. The ordinary-turned-sinister? Dummies! A very British bleakness? Clive dies in front of his wife and son. Jokes? The London Eye. A lack of sci-fi technobabble? Anti-plastic.

"And so on, each moment carrying a bigger agenda."

Doctor Who - Rose (2005)

For me, the episode works brilliantly in its smaller moments. The crisis in the pizzeria when Rose instinctively hits the fire alarm, sending her fellow diners out of harm’s way and immediately showing how resourceful she could be. Christopher Eccleston (underrated to this day) somehow managing to show the pathos, depth and feeling of his Doctor with one gripped hand on a council estate.

And even today, having watched Rose a dozen times or more since 2005 I’m still struck by how fun and exciting that episode is. What a pilot! What a story! No wonder we’re all still chatting, laughing and arguing about Doctor Who.

Is Rose a perfect episode? In a way, yes – it’s perfect at doing what it’s supposed to do, and even if you’re irritated by a burping bin, a plastic p-p-pizza lover or some rushed exposition, the episode will zip past it a moment later. If it was released today I still think it’d be considered a belter of a story (as we may all see when fans rewatch the episode together with Russell T Davies).

Doctor Who: Rose

But even if it didn't entirely stand up to the test time, the value of Rose to Doctor Who as a whole is incalculable. When you go on BBC iPlayer to watch any episode of Doctor Who, I find something quite touching about the fact that the whole thing automatically redirects you to Rose as the first episode.

As fans we often think of Doctor Who in "eras" – the Capaldi era, or the Moffat era, broken up by Doctors and showrunners – but really, it’s all the same show. No matter what changes in front of or behind the camera it’s one ongoing story.

For the modern series, that story began again with Rose. It’s easy to see why we all kept watching.

Find out how to join in with the fan rewatch of Rose here. For more TV picks, check out our TV Guide.