Greg James: 'It's nice to be nice, isn't it?'

It's a Thursday evening in the Radio 1 studio, and Greg James is playing a pre-recorded interview with the R&B star Usher. The pair compare the 'recent calls' list on their mobile phones: Usher reels off a list of the musical A-list, while on James's list are his parents and a non-famous friend. When the interview ends, James plays Usher's new track, while quickly cutting a quote from the interview, so that he can play it in the following link, and mimic the singer's southern US drawl.

This is James's style: he plays the ordinary person in the face of celebrity, his relaxed delivery peppered with self-effacing stories, funny voices and an unashamed technical geekery when it comes to the studio equipment that many other radio presenters don't bother with.

While I'm there, hundreds of tweets stream in from the nearly six million listeners, with requests, praise and, occasionally, requests for dates.

According to his producers, tweets have overtaken texts as the younger listener's missive of choice, with the ratio of tweets to texts revealing how old the audience are. Happily for both presenter and station, they are young. At 26, James falls in line with the Radio 1 under-30 demographic, and his promotion this year to the drive-time slot at the expense of the well-liked Scott Mills (aged 39), was seen as one of the most visible moves by the Radio 1 management, after much criticism – not least from the BBC Trust – that the station's listeners (and presenters) were too old. He's also had his fair share of press attention for a celebrity romance with the pop singer (and royal wedding performer) Ellie Goulding.

After the show, we sit in the tired-looking basement studio with its glaring Radio 1 sign. It's a world away from the glamour that the teenage fans might imagine.

"I'm just a show-off really," he says when we sit down. "I like having the reaction of a crowd, and I like making people laugh."

His approach seems to be working for his growing listenership and his 645,000 followers on Twitter. A producer jokes that James has lots of polite, middle-class teenage female fans called Poppy. And it's not difficult to see why: he's tall, quietly confident, nice-looking and well, just nice. As celebrity crushes go, he's in the small category of the ones that you could also safely introduce to your parents.

While he is now full of the confidence that his job both requires and engenders, it wasn't always the case. When he was first hired to do the pre-breakfast slot on the station, he was a 21-year-old barely out of his previous gig as the student station manager of the University of East Anglia's 'Livewire' radio, who spent his summers working at stations across the region.

"I was on before this bloke I had listened to at school – [Chris] Moyles. I spent a good year and a half trying not to panic, because I was handing over to him," he says. "He'd be suddenly there and listening to my last link and I'd be thinking 'I hope he liked it'. That was very difficult: moving to London, being 21, not knowing what you're doing, not really knowing London, not knowing how the radio industry works, you just don't really get it. But Radio 1 were really great with me, they just let me grow up, I suppose, in my own time. And you wouldn't get that on a commercial station necessarily. They took a chance on me, they nurtured me and I was very lucky with the producers I worked with."

Reaching the heights of the Radio 1 Drive Time show by the age of 26 is no doubt a fine achievement, but the job he had been widely tipped for was to replace the man he used to open for, Chris Moyles, as the host of what had been the country's biggest radio show. After much press speculation, the gig went to the less-tipped Nick Grimshaw. So much has been made of his "losing out" to Grimshaw that he now agrees that being asked how he feels about not landing the breakfast gig is far more annoying than missing out could ever have been.

"I want to get a big banner, that says 'I'm OK'," he says, with a hint of frustration. "I don't know how many more times I can parade it to people… I don't see how things could go much better for me at the moment, I wouldn't be able to cope with things going better right now.

"There's some guy on Beacon FM who's gutted he's not on Radio 1. But for me… how dare I sit here and say [adopts a whiny voice], 'Oh, I'm so unlucky, I only got Drive Time'. What sort of twat would I be?"

He is at pains to portray himself as one who is still in his radio apprenticeship, insisting that he is still learning, and referencing those who inspired him – be it the achievements of the Chrisses (Evans, Tarrant and Moyles), his desire to follow Dermot O'Leary's career path, or quoting Terry Wogan's autobiography.

There are definitely a few 'Poppies' in the audience when we next meet at the Friday night recording of Unzipped, the BBC3 TV show he hosts with Russell Kane. Formerly Britain's Unzipped, under the auspices of discovering what Britons do in secret, it is a bit like a televised version of Truth or Dare, with embarrassing revelations from both the audience and celebrity guests.

Onscreen, James and Kane appear a conventional double act. Kane runs around the studio like the attention-starved lovechild of Russell Brand and Noel Fielding, while James plays the straight man, getting his laughs around the edges.

Despite a few sex jokes that Poppies wouldn't want to repeat in front of their parents, his humour remains within the safe category.

"I wanna be Mr Mainstream," he says in his dressing room afterwards. "I'm not particularly trendy. I wanna be relevant and relatable and 'cool' and young for Radio 1, but I'm not trying to be alternative or anything.

"You can still be not boring and mainstream, without [being] offensive and sacked. I think on my Radio 1 show I say things that maybe I shouldn't, but you can kind of get away with it if you do it in the right way."

His hope is that if he continues to "do it in the right way", he will land the sort of Saturday night BBC shows he watched growing up.

"My big dream is just big Saturday night shows," he says. "A Noel's House Party, TFI Friday, big shiny floor-type show, big chatshow-y show. Like Unzipped, but on a bigger scale really, and live."

This desire was first inspired, aged eight, when his mother took him to Television Centre to see the set of Noel's House Party. He later learnt the basics of radio aged 14, while playing with the equipment and listening to other presenters at Stortford Radio at Herts and Essex Hospital. Then, he was the less Radio 1 sounding Gregory James Alan Milward. He dropped his last two names when a friend at university suggested he have a "DJ name".

It's easy to tell how close he is to his family; his parents are retired, but his father, Alan, was a headmaster and his mother, Rosemary, a special needs teacher. He and his sister, Catherine, who works in recruitment at Deutsche Bank, recently decided to take over their parents' mortgage – one of the few ambitions he had when he became financially secure.

"The three things I wanted to do were sort out my mum and dad, so they can stay in their house forever, get a car and get a flat and that was it. And that's kind of done." The issue of his parents' mortgage was obviously important to him. "I like making sure that they're just fine, because they put me and my sister through university and that kind of stuff. I don't feel like I owe them… It's just nice to be nice, isn't it?"

This niceness combines with a personally-calibrated moral compass which decides what he will do off-air, be it DJ-ing club nights, or choosing brands to endorse.

"I would never do anything for the money, ever," he says. "There was a big sweets company, wanting me to be the face of their big marketing thing last week. And they offer stupid money for stuff like that, for a day's filming. The sweets were really nice and the money would be… fine. But I wouldn't be excited. I'd wake up and go, 'No, I don't want to go and do this'."

He refuses to say which company this was, but a few days later I come across an online advert for Maynards with a picture of Harry Judd from the boyband McFly tied to a lamppost. Were this the offer, James was possibly right to give it a miss.

"My gauge is, what would the 15-year-old extra-nerdy version of me, who wanted to get into radio and presenting TV programmes, think of the 26-year-old version of me?" he says, considering his beer. "I don't want that person to be disappointed with me, basically. I don't want my listeners to think that I'm not being honest or normal – I think that you can lose touch."

His friends are still the friends from school and university, bar the addition of Russell Kane and a couple of members of the England cricket team, he isn't often seen on the celebrity party circuit and doesn't seek out publicity or the paparazzi like some of his peers. At present, he's single, though he found himself in the spotlight earlier this year when his split from the folk singer Ellie Goulding became the stuff of tabloid gossip columns. Given the fact that attention returned when the news came that he wasn't getting the Radio 1 Breakfast Show gig, it seems that he is someone the tabloids would perhaps like to become a regular feature. While he is confident that his behaviour wouldn't warrant any negative press, it's not, he says, a game he is particularly keen to start playing.

"If they want to write about me, I have no problem at all," he says. "As long as I'm represented fairly, I don't care. If I'm linked with a famous person, as long as it's truthful, I don't really mind…" Before adding, matter of factly, "There's no reason for them to be nasty, and if they were, I'd fucking take them apart on the radio the next day! I'm not actively resisting it… but I'm not fussed by it, and I won't go searching for it… I wouldn't turn up to something to get mentioned."

Despite being single, he doesn't seem to offer much hope for any groupies. Visibly embarrassed, he tells a story about the previous night, where his cab driver expressed shock that he hadn't "caught a fish" (the driver's phrase for picking up a girl) after a DJ gig at the Ministry of Sound.

"There's a weird expectation that you're supposed to go home and sleep with all your groupies. But I would be utterly depressed in the morning if I did that – why would I want to do that?"

Rarely, however, do those who claim not to care how they are portrayed, actually feel entirely that way. James must have some notion of his public image, or he wouldn't have agreed to this, or any other interviews. And his personality is inextricably linked to his ever-growing career – so how does he want to be seen?

"It's not like I'm like a pop star – I don't need to sell albums. I just need people to buy into me as a person. If people are interested in me and what I'm saying, if people are interested in this [the interview], people will know that I am the real deal and I haven't just stumbled into a radio studio. People will build up a picture of it and decide whether they like you," he says, before adding with a smile, "If they don't, they can fuck off."

Greg James will broadcast live from the BFBS studio in Camp Bastion, Afghanistan, from Monday to Friday, 4pm-7pm