Making the kids’ tea is not usually a traumatic event, but last Monday I had to stop. Too many tears. On Radio 4’s PM, the journalist Steve Hewlett was being interviewed by the presenter Eddie Mair; Hewlett was describing his recent wedding. It had taken place three days earlier, organised within an hour. Speed had been essential because Hewlett, who has cancer, had been told by his consultant that he might not last. This was a shock: to Hewlett and his family, but also to PM’s listeners. He’d seemed to be responding well to treatment, and suddenly the whole story had shifted.

Yesterday, on the phone from his home in Harpenden, Hewlett says: “It was a shock. On the Wednesday, in the afternoon, I’d finished doing my interview with Eddie and, as far as we knew, I was having my second dose of immunotherapy the next day. That was the takeaway for the interview. But then my consultant came back and she told me that we’d got as far as we can get. I asked what that meant. She said, ‘It means we’re no longer trying to save your life from cancer, because we can’t.’”

Hewlett, pauses, to give the punchline. “Unfortunately, the diagnosis happened at 5.15pm. Eddie left at 3.30, so he missed it. He had to come back on Monday!”

For several months, Hewlett has been popping up on PM, giving listeners an account of his cancer (it was initially found at the bottom of his oesophagus). He has also been writing about his experience for the Observer, in his My Cancer Diary series. A BBC man of many years’ standing – he was Panorama’s editor during the 1990s, and has presented The Media Show on Radio 4 since 2008 – Hewlett has approached his diagnosis and subsequent treatment with a journalist’s thoroughness. He has researched on Google, talked to friends who have been through cancer, investigated where best to get treatment, listened to and challenged his doctors. Whatever he has encountered, he has almost always been prepared. In an early broadcast, when he questioned a registrar over his prescription, he was allowed an extra drug, one that gave him 10% more chance of survival. “I think I just prescribed myself,” said Hewlett to Mair. To me, he says: “The more engaged with your treatment you are, the better treatment you get.”

Over the phone, Hewlett’s voice is croaky, but his mind is as sharp as ever.

“My situation is acute,” he says. “I can go at any moment. But it doesn’t feel like it to me. This morning, I felt a bit queasy, and I have a few aches and pains, but otherwise I don’t feel compromised. My brain doesn’t feel like it doesn’t work.”

As the programmes have continued and Hewlett has gone through radiotherapy, chemotherapy, drug trials, immunotherapy, interesting relationships have developed. The first, fundamental one, is with Eddie Mair. When Hewlett approached the head of Radio 4, Gwyneth Williams, with an idea of reporting on his cancer, she suggested that it become a slot on one of the station’s stalwart shows. PM was quickly fixed on, and it has proved an inspired choice. Mair and his producers have allowed the interviews to breathe. Hewlett said he almost panicked when Mair informed him they had 15 minutes to fill on the first show, but Monday’s interview was 25 minutes long, and not a moment was wasted.

Though Mair doesn’t speak much during the interviews, his tone is perfect. He knows when to lift the mood with a joke, when to ask for detail. And Hewlett likes detail, and truth. The combination of the two men has made for gracious, realistic and very touching radio. “I don’t think you often hear men talking about cancer,” he says. “And Eddie has a way with words, and a manner that every now and again opens up a whole new vista.”

Hewlett has enjoyed another combination: that of writing and broadcasting. Broadcasting comes more naturally to him – “it gives you more control, in a way” – but he’s found that his Observer diaries have meant that he can deal with wider themes, “take the minutiae and spin them into a bigger point”. These points are varied, from moods (“my uncertainty”) to practicalities (“side-effects and what that actually means”).

We talk about how when you’re involved with hospitals, your reality keeps changing. One moment you’re on a drug trial, then you’re not; one moment you’re having immunotherapy, the next, there’s nothing more to do.

“You’re always making decisions,” says Hewlett. “Almost every week, there’s a moment where you have to consider the next move, take a perspective. And with most of these things, it comes down to probability, it’s chance. The experts have a certain knowledge, accumulated over years, and it’s as reliable as it can be … But beyond that, it’s all chance and hunches. Are you qualified to make the decisions? Well, you don’t have the experience, but they don’t have your instinct. They don’t know how you feel.”

Which brings us to another interesting relationship, that of Hewlett with the Radio 4 audience. He has been genuinely overwhelmed by the response: hundreds of letters have arrived at the Royal Marsden, where he has been receiving treatment, social media has been full of tributes, and PM has been broadcasting some listeners’ reactions. One woman took her husband to the doctor because of Hewlett’s broadcasts (and yes, he did have cancer); others have spoken of how the interviews have guided their own discussions with family members in treatment.

“The main thing I wasn’t ready for was the reaction of listeners,” says Hewlett. “I wanted to open myself up, to talk about what has been happening, but I didn’t imagine people would get as much from it as they have. Radio 4 talks a lot about having a relationship with its audience, how precious that is. This is the Radio 4 audience in top gear. That’s what it feels like to me.”