I asked the Prime Minister why Andrew Mitchell kept his job for so long.
"It's the easiest thing in the world if you're Prime Minister just to fire someone as soon as something goes wrong," he said.
"But that's not the right way to behave as Prime Minister. He did something that was wrong, he needed to apologise, he did apologise."
He said Mr Mitchell had resigned when it became clear that he would not be able to continue as an effective Chief Whip.
"The time it takes might be uncomfortable and difficult for politicians and governments...but in the end, government is about doing the right thing, making the right decision, not just making the easy decision," he said.