What do Phillip Schofield and Holly Willoughby really think of each other?

Their laughter is chaotic and unpredictable, generally occasioned by an innocent double entendre, like the time chef Gino d’Acampo cooked sausage-in-the-hole or when they had to introduce an item about Gwyneth Paltrow’s “tidy pantry”.

“They’re never planned,” Schofield says when we meet one morning just after the duo have come off air. We’re sitting in a cramped dressing room backstage at the ITV studios on London’s South Bank and both of them are still in their on-screen make-up: faces inch-deep in powder and fake tan.

“Because we have the same sense of humour, it works at the same speed. We think the same thing, more or less, we laugh at the same stuff. So, you know, if you write in a script anything about Gwyneth Paltrow’s tidy pantry, it’s going to get us both at the same time.”

“It’s going to tip you over the edge,” Willoughby agrees, sitting next to him on a low sofa, sipping on a cup of tea.

“And then one goes and it makes the other one worse and then that makes the other one worse,” adds Schofield. “So it builds.”

“And suddenly you just can’t remember what you’re giggling about,” concludes Willoughby.

They’re laughing again now, egging each other on. It seems they genuinely can’t help it. Sometimes, she will give him “a little nudge” when there’s a “slightly naughty or slightly rude” phrase in the script. Today, it happened when she had to say “two ways with rhubarb” and Schofield could barely contain himself.

“I have a very limited ability to stop myself from laughing,” he concedes. “It’s very easy to push me over the edge.”

Schofield and Willoughby know each other’s weak points. In fact, they know each other so well, Willoughby claims to be able to intuit what he is thinking. They go on holiday together, they hang out with each other’s families and Willoughby can make Schofield a margarita that meets his exacting standards. How does he like them? “Strong!” she says.

The two of them have presented This Morning together for eight years. Before that, they fronted seven seasons of Dancing on Ice, so all in all, they’ve been a partnership for longer than many real marriages last.

The ever-discerning readers of RadioTimes.com have just voted Schofield and Willoughby their favourite on-screen couple. “We were surprised when we won because Ant and Dec were in the mix and no one beats Ant and Dec in anything,” says Schofield.

What’s the secret to their success? Well, essentially it’s that there is no secret. Both of them claim to be exactly the same on television as they are in their normal lives. Certainly they seem easy and relaxed in each other’s company.

Willoughby, 36, is warm and bubbly, all floral print and long tumbling blonde locks. The 55-year-old Schofield has a slightly sterner manner and is more reserved than I’d anticipated: the silver-haired older brother to a cheeky younger sister.

“I think that if you watch This Morning on a regular basis then you get an insight into our friendship, which is the same on screen as off,” says Schofield.

“We have a laugh.” Willoughby nods. “It’s also the nature of the show,” she adds. “It’s two hours, live, every day. So it’s like we don’t give people the option [to like us or not]. We’re in your house for two hours!”

Viewers hold them in such deep affection, that even when they turned up slightly the worse for wear to present This Morning the day after winning a National Television Award last year, no one seemed to begrudge it.

Both of them were still in the same black-tie clothes from the night before and seemed to be staring somewhat blurrily into the autocue. There were empty champagne glasses cluttering the on-screen coffee table.

“We just had to get through it,” Willoughby says now. “Whoever was watching had voted. It was kind of their fault.”

The two of them had gone back to Ant McPartlin’s house to celebrate after the awards ceremony and had ended up playing a game of Pie Face.

“You’ve got your head through a mask and there’s a little spoon thing in front of you and it’s full of cream,” Schofield explains. “Then you turn a little dial and you turn it and turn it, and you never know when it’s going to go and then finally it will flip up and it will dump this lot on your face. That’s all well and good, but then you start to ramp up the pressure. You put piccalilli on it.”

Willoughby is laughing now. “We just went to the fridge and found jars of stuff.” “Chilli oil,” Schofield says. “I got chilli oil in my eye.”

It’s why, if you look carefully at the footage, you will see stains of yellow on Willoughby’s white designer gown. She thinks it was piccalilli. Or mint sauce. Neither of them can really remember.

Anyway, they didn’t get into trouble and it’s not an incident that’s ever been repeated, although, as Schofield says, “Never say never.”

Apart from these occasional lapses, they are consummate professionals: coming in each morning, reading their scripts in the car, being briefed on the guests and then writing their own questions for every interview segment.

Often, when they compare questions, they find they’ve written down exactly the same ones. “Career-wise he’s kind of guided me,” she says. “We spend quite a lot of time together and quite often I’d come in in the morning and I wouldn’t have slept properly because of the kids [Willoughby has three with her husband, TV producer Dan Baldwin] or something and he’s my first port of call to talk to, really.”

“Holly is incredibly sympathetic,” Schofield says. “She’s the best person to tell secrets to. She’s got a brilliant ability to see sense through mess. She’s also more diplomatic than I am.”

It’s lucky they have such chemistry. Have they ever wondered what it would be like to do this job with someone they secretly hated? “I think it would be really hard,” Willoughby replies, “because it would just drive you mad. I just don’t think you can.”

“You could do,” Schofield says, “but it just would not be any fun.” They catch each other’s eye and start to giggle. It’s clear they have fun, both on and off screen. Even better: we have fun watching them do it.

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