By Kevin Young
Entertainment reporter, BBC News
It is a minute to five on a Sunday afternoon. Millions of people have retuned their radios from crackly medium wave to crystal-clear FM.
Radio 2's Sing Something Simple gives way to the pips, and the Top 40 explodes into life on Radio 1.
At home, "record" buttons are pressed, battered C-90 cassettes whirr, and if mum tries to serve tea before seven o'clock, she is in big trouble.
"The Top 40 was the absolute flagship show," says former host Richard Skinner.
"At the time, it was claimed as the most listened-to show in Europe. I don't know how we calculated that, but we certainly used to say it."
He says that to listen in stereo - when Radio 1 did not have its own FM frequencies - made it "sound even more important" and provided "an extra sparkle".
The show began as Pick of the Pops on the Light Programme in 1955, with Alan "Fluff" Freeman hosting throughout the 1960s.
"Fluff" Freeman hosted Pick of the Pops for Radio 1's first five years
But the launch of Radio 1, 40 years ago this Sunday, saw its duration double to two hours, and the start switched to five o'clock.
"Younger people now perhaps wouldn't appreciate just how dominant it was," says David Jensen, who in 1984 would launch the rival Network Chart, which combined sales and airplay.
Jensen says his move to commercial radio came "at a good time" because Radio 1 wanted him and colleague John Peel, both presenters on weekday evenings, to swap slots.
"Neither of us was particularly happy about this, and we had long, fraught discussions about what would happen," he says.
Skinner admits Radio 1 was "arrogant" in those days and "genuinely thought there was no competition".
"We used to say things like, 'Well, isn't it marvellous - there's David Jensen playing the same records in a different order.' But clearly what he was doing was the beginning of a change."
Goodier gave up when chart shows were "all people thought I could do"
Two DJs who became synonymous with the Radio 1 chart were Bruno Brookes and Mark Goodier.
Brookes hosted from 1984 to 1990 and was replaced by Goodier for 18 months, before returning in 1992.
Brookes calls the programme "a milestone" in his career, which he tried to make as "energetic" as possible.
"It was important to give equilibrium in terms of the excitement to all acts or bands. I thought it was only fair."
Goodier says he had "a bit of a problem" with being taken off the show in 1992, when bosses insisted he could not present the Top 40 and new music show The Evening Session.
"I said, 'I can, because I've been playing all these new bands, and when they get in the chart, that's a validation of what we've done.'"
Capital Radio recruited David "Kid" Jensen to host its Network Chart
He returned to the slot between 1994 and 2002.
Goodier admits there was "definitely" rivalry between him and Brookes.
"I think he was a very good jock and had a very big fan base.
"I came about it from music, and I think he came about it from showbiz, and did it really well. I've no criticism of him."
Commercial radio capitalised on unsettled times at Radio 1 in the mid-1990s, when controversial changes meant the departure of several veteran DJs.
"We were a personality chart that was a really fun show, with competitions, interviews with the stars making the hits and montage recaps," says Neil Fox, who took over the Network Chart in 1993.
"If you listen to JK and Joel on Radio 1 now, it's everything the Pepsi Chart was 10 years ago."
The audience for the commercial radio chart would eventually overtake Radio 1, something which Goodier regrets.
"There was a very sad era when the chart was not a priority for Radio 1, and they did consider taking it off," he says.
"They opened the door to the commercial radio chart gaining in strength. In the end it was on more than 100 stations."
Neil Fox says commercial radio was happy to "champion" his chart
However, Fox admits he is not a fan of Hit40UK, the show which has replaced his.
"They ruined the whole thing. They thought they needed to change for the sake of it, and Radio 1 now has the biggest chart again."
Of course, things could go wrong on such a high-pressure programme.
Skinner - who once edited Sister Sledge's hit Frankie down to less than two minutes for the countdown because he hated it so much - recalls introducing Black Lace while their single was still in its sleeve.
An error with Madonna's Vogue led to Brookes drowning his sorrows
"We played the jingle and I said, 'Oh, hang on a second, I haven't put the record on.' I got the record, threw the stylus on and it started at once - God obviously loves Black Lace."
Brookes once accidentally included the expletive-laden unedited version of Rage Against the Machine's Killing in the Name on the show.
But something else which "sticks out like a sore thumb" for him was playing one chart-topper - Vogue by Madonna - a song too early.
"I had to get to the pips at seven o'clock with the number two song. It was so embarrassing that me and my producer went round the pub and got drunk."