Boris Johnson, reelected last year as London’s major and often discussed as a potential Tory successor to prime minister David Cameron, had a very bad weekend.

In an interview with the BBC’s Eddie Mair, Johnson hemmed and hawed over whether he once invented a quote 30 years ago as a young news reporter, lied to former Conservative leader Michael Howard over an affair and a controversial phone conversation from 1990 between Johnson and a friend who wanted to, perhaps, assault a journalist (the journalist was never assaulted, though), each of which are revelations to be discussed in an upcoming documentary about Johnson’s life.

The interview culminates with Mair asking, ‘you’re a nasty piece of work, aren’t you?’

Mair finishes the interview challenging Johnson’s integrity even further for refusing to answer whether he wants to be prime minister one day.

I’m not sure that the questions were entirely relevant to Johnson’s role today as a two-term mayor of London, but it was nonetheless painful to watch Johnson dissemble throughout the interview, especially given the easy manner that ‘Boris’ generally has in public, which was clearly on display during the 2012 summer Olympics.

I’ve seen bad interviews before, and this is about as bad as the infamous Roger Mudd interview with the late U.S. senator Ted Kennedy in 1979 when Kennedy couldn’t give a compelling answer as to why he wanted to be president (Kennedy was challenging U.S. president Jimmy Carter at the time for the Democratic Party’s nomination).

The interview doesn’t necessarily end his chances to become prime minister one day, and it may well backfire on Mair, but it will also certainly renew and reinforce existing doubts about the London mayor’s discipline and his image — it’s the downside to the boyish, off-the-cuff charm that has made him such a noteworthy foil to the more dour Cameron and his chancellor of the exchequer, George Osborne.

Watch the choice clips from the interview below the jump: