Shock start for Radio 1 breakfast host Nick Grimshaw

He had been a guest on the flagship show to chat about his appointment but Moyles and his team played a prank by walking out, leaving the new boy muttering: “This is so cruel.”

Grimshaw revealed he almost blotted his copybook just as he was about to be given the job by telling station controller Ben Cooper he “just can’t function in the morning”.

The 27-year-old was announced as the new breakfast host on Wednesday shortly after Moyles told listeners he was moving on after eight-and-a-half years fronting the show.

Party boy Grimshaw said the last few hours had been “surreal” as he got to grips with landing the biggest job at the station.

But when he was called into a meeting with “big boss Ben” on Tuesday, he had feared he was facing a reprimand.

“When I went for the meeting at 9:30, which is early for me, I went into the meeting and I was late and I thought I was going to be in trouble. My agent knew and said it’s not trouble.

“And I went in and said I’m  really sorry I’m late Ben, I just can’t function in the morning. And he went ‘OK’.”

Mr Cooper has said that he wants Grimshaw to present the programme on his own, and move on from the “zoo” format of Moyles’s show in which his production team play a large part.

So outgoing host Moyles – who will quit the show in September – put him to the test by walking out of the studio with the rest of the crew, leaving Grimshaw to fill the airtime alone.

“Everyone’s gone – this is not a hilarious on-air radio gag,” he said.