Boris Johnson had a terrible old time of it with Eddie Mair this morning.
It's so rare to see Boris submit himself to difficult interviews, that there was genuine shock from commentators on both the left and right at his performance.
The questions were not even that hard. They were all about controversies that happened long before he became mayor. They should have been incredibly easy for him to bat away.
That he couldn't is a sign of just how little used he is to serious scrutiny.
There are only four interviewers that Boris will regularly face for sit down interviews.
One is Andrew Marr who typically asks him very predictable questions about David Cameron and national politics.
The second is Jeremy Paxman, who is a good friend of Boris's, and usually just asks him knockabout stuff about wanting to be Prime Minister.
The third is Nick Ferrari on LBC radio and the fourth is Vanessa Feltz.
This is no accident. Boris's appearances are strictly controlled by his team.
Regular mayoral press conferences were cancelled right at the start of Boris's time in office and are only very occasionally held now.
Boris has refused countless invitations to appear on the London section of the Sunday Politics show and has only agreed to one interview with BBC London's political editor Tim Donovan in recent years.
During the last mayoral election, BBC London were denied access to him and were not even sent press releases saying where he would be from day to day.
Boris's team even threatened the BBC with a "wave of attacks" from "our friends in the papers" if they broadcast an interview with Boris's biographer Sonia Purnell.
None of this would matter if the press did their job, but the only newspaper to regularly cover his mayoralty is both owned and edited by his close friends.
As a result, Boris has become battle soft.
As I wrote in my piece for MSN News this weekend, Boris is just not used to being under fire.
When he does come under attack as he did at a disastrous appearance in Catford earlier this month, he handles it very badly indeed.
The main reason I find it hard to see Boris ever becoming Prime Minister is that I just don't think he would be very good at it.
Anybody who watched the hustings at the last mayoral elections, or sees him at his monthly mayor's question times, will have seen that he is actually a pretty poor debater.
Boris is great at the flag-waving stuff, and is always good for a colourful quote, but I just find it difficult to see him coping as the leader of the opposition, let alone as Prime Minister.
David Cameron may not be as likeable as Boris, but he can hold his own in the House of Commons. He can deal with difficult questions in interviews. He is just a much more professional politician.
Boris's lack of professionalism is a big part of his appeal of course, but I'm just not convinced it would survive the intense scrutiny of being a major player in national politics.
Boris has already had one parliamentary career. It was largely a disaster.
I see no reason to believe that his return would be much more successful.
Read my piece for MSN: Boris Johnson: world king or emperor with no clothes.