Affair of the Heart: Jamie and Harriet are still the capital's favourites

Despite the anodyne music and the stiff competition, Heart FM's early morning duo Jamie Theakston and Harriet Scott are still the capital's favourites. Ahead of the Sony radio awards, Ciar Byrne sits in with them to discover why – and hears the truth about their famous toasters

Breakfast banter: Jamie and Harriet have been perfecting their act for the past three years © Will Wintercross

As the Scissor Sisters fade out, a caller comes on air to tell Harriet and Jamie about her pampered cat – the pet is so spoilt that she even cleans its bottom with baby wipes. It is 8.55am, the end of a three-hour shift for Heart 106.2FM's Jamie Theakston and Harriet Scott, who – until Thursday at least – hold the crown in the competitive 6am-9am slot in London commercial radio.

In the studio, Scott is the livelier of the two – dancing around in her chair to 80s pop classics – although that may have something to do with Theakston's lack of sleep. He has just returned from paternity leave after his wife Sophie Siegle – the manager of the private members' club Soho House – gave birth to their first child, a son called Sidney.

"I'm not getting much sleep," he admits. "Doing this job and having a week-old baby, I'm getting about an hour a night. When he's crying at half past three, I think, 'I've got to go to work in an hour'." Once exposed by the tabloid press for visiting a prostitute in a Mayfair brothel, Theakston these days is in bed by 9pm in preparation for a 4.30am start.

Before the show goes on air, the pair, together with their producer Jamie Scott, leaf through the day's papers, picking out stories to discuss in links. Beside Theakston's terminal sit The Guardian and The Times, while Scott's reading material of choice is the Daily Star and the Daily Express. "Harriet is the only person I know who reads the Express," says Theakston.

Although they can both "drive" a desk, Scott and Theakston are not responsible for playing records. Instead, they sit on high stools in front of microphones, giving them time to plan their links between songs. "We get through an awful lot of material," says Scott. Theakston adds: "We have to generate about 40 things every day. You have two and a half minutes to think about what you're going to do – the song is your thinking time."

Evolved over three years now, their relationship is affectionate, but nevertheless teasing. Theakston says: "It's the sort of dynamic that all good comedies have worked on. The way in which men and women have different opinions on things, whether it's a husband-and-wife dynamic or a brother-and-sister dynamic. I think it's important that the man shouldn't be overbearing."

They take it in turns to lead the link. "When you're on your own, you can just freefall, but with two people you have to know where you're going. After three years I think we understand each other," says Theakston. Scott started out as a solo presenter, but now believes she would feel "lonely" in the studio on her own.

The breakfast hosts have little say over the playlist, which is an exact science based on feedback from listener focus-groups who prefer unchallenging pop ranging from Take That to Luther Vandross. "We're still playing on a fairly high rotation Leona Lewis's 'Bleeding Love'," says Scott. "It's a great song, you might think people would be sick of it, but it appears not."

On the morning I sit in, they play Rick Astley's "Never Going To Give You Up", and Theakston is almost rude about it, asking how many Astley songs listeners can name. Afterwards he insists he is an Astley fan: "in my Next suits I dance around the front room".

When Scott gets home, she counters the morning's diet of pop by trying "to be cool and listening to the Raconteurs". Away from the studio her routine is different from Theakston's and she tries to sleep during the day. "It means I can have a decent evening, have dinner with my boyfriend and socialise a bit and go to bed at 10.30."

The typical Heart FM listener is a 34-year-old woman with young children. "It's good for the show that Jamie has had a baby," says Scott. "It's the only reason I had a child," he jokes. Listeners clearly feel they have a personal relationship with the presenters. Theakston has been inundated with congratulatory emails and one listener has even written and recorded a CD of six lullabies specially dedicated to his baby son. Scott says, "We're in people's bedrooms and living rooms for three hours; it's much more personal than a TV show. Listeners feel they know Jamie and want to know about Sidney."

At next month's Sony Radio Academy Awards, Theakston has been nominated for Radio Personality of the Year. He seems a little embarrassed by the nomination. "It seems odd to be nominated personally for an award that's really for both of us."

The former Top of the Pops host still returns to television to present one-off events including the Diana Memorial Concert and Sport Relief, both for BBC1. His last TV series was The Search on Channel 4 – a sort of reality TV version of The Da Vinci Code, which took two years to put together, a far cry from the immediacy of the radio studio. Does he feel more comfortable on television or radio? "I started in radio and when I did my first TV show everyone said, 'what's it like doing TV when you're a radio person?' Then I started doing this and they said, 'what's it like doing radio when you're a TV person?'"

It is not entirely clear whether or not he is joking when he adds that the only reason he joined Heart FM was because he was "terrified of not working".

"It's all about maximising your revenue. You're always terrified of not working. At any moment that could be it," he says.

Theakston has also worked in radio for the BBC on Radio 1 and Five Live and does not share the usual commercial-radio gripes about the corporation's dominance of the airwaves. But he does feel some of the regulations imposed on commercial stations are unduly restrictive, including the obligation to "localness".

That does not mean he does not enjoy catering to a London audience. Born near Brighton, Theakston moved to London at the age of 18 and lives in Notting Hill, just around the corner from Heart's HQ.

Scott, who was born in Yorkshire and has lived all over England – "like The Littlest Hobo", says Theakston – moved to London a decade ago. "Because of my childhood, when I moved around a lot, I couldn't wait to come to London. It's a place where you don't have to be born here to fit in. I do feel that this is my home. I don't ever want to leave now," she insists.

Living centrally means the pair can fit in plenty of movie screenings. The film industry is an important source of guests for the show, whose listeners apparently like nothing better than to watch a good DVD at the weekend. After our interview, they are off to conduct an interview of their own with Gwyneth Paltrow, whom they plan to talk to about living in London. While Theakston was on paternity leave, Scott interviewed George Clooney. Other guests have included Kate Hudson, Will Smith and Scott's personal favourite – Kermit the Frog. But the job is not always as glamorous as it sounds.

Scott says: "You don't get long with these people. You get seven or eight minutes. I think because we're non-threatening, sometimes we get more out of them."

She did manage to upset Morgan Freeman – "I asked him if he had a tattoo and he said, 'yes', and I said jokingly, 'I'll show you mine if you show me yours', so he showed me his, and I don't have a tattoo."

The listeners' attachment to the station is reflected by the enthusiastic response to phone-ins and quizzes. Contrary to expectation, it is not the competitions with the best prizes that always attract the most entrants. One of the most popular prizes is the Heart breakfast toaster – which leaves toast embossed with a heart shape. "Have you seen the Heart breakfast toasters? They're rubbish," says Theakston, before being quickly hushed by Scott and the radio station's PR manager.

The show operates in a tough market, recently made even more competitive when Denise Van Outen joined her old sparring partner Johnny Vaughan in the mornings on rival Capital 95.8FM. Now, in a strange twist of events, Global Radio, the private company that bought Heart's owner Chrysalis in July 2007, has agreed to buy Capital's owner GCap Media.

Theakston does not seem too concerned about what this will mean for the future of the two stations. "Both the Capital and Heart breakfast shows are very successful, so I'd be surprised if it made much sense for them to try and change them," he says.

There are parallels between the two shows. Like Vaughan, Theakston is probably best known for his television work, although he started out in radio as a wannabe sports presenter on GLR, before moving into children's TV shows such as The O-Zone and Live and Kicking. The two pairings are also similar in age – Theakston and Scott are 37 and 33 respectively, compared to Vaughan and Van Outen's 41 and 33.

The Heart FM duo takes the competition seriously. "It's very important to understand what other shows are doing, so we do listen-backs," says Theakston. Scott quickly chips in, "Equally, you just have to crack on and do your own thing. We've been doing this for three years. We've found a good groove, so we just keep doing it and don't have any knee-jerk reactions."

They are clearly on a level footing. Theakston may be the more instantly recognisable, but Scott is an extremely experienced radio DJ who worked her way up through local radio in Reading, Hull and Birmingham before joining Virgin and then Heart, where she originally teamed up on the breakfast show with Theakston's predecessor Jono Coleman.

Does it ever all go horribly wrong? That morning, Theakston and Scott were forced to go to a song when a competition caller failed to come on the line – a rare occurrence.

Scott says, "That doesn't happen very often and it's very easy to rectify. That comes with confidence. It's not brain surgery. It doesn't really matter if they're not there. You have to think, 'how long are we going to leave this dead air hanging here?'"

Unlike on live television, Theakston insists it is difficult to mess up seriously on radio. "It's like if you were in the pub, chatting to your friends, where you don't make a mistake during your conversation."

Heart Breakfast goes out 6am-9am weekdays on Heart 106.2FM, and on Freeview, DAB, and heart.co.uk