"I cannot swear that I've always observed a top speed limit in this country of 70 mph," Johnson says after being asked by ITV if he has done anything illegal.
The question was a nod to rival contender Michael Gove's admission that he took cocaine as a young journalist.
But Johnson goes on to swerve the query, saying the key issue is that he does what he promises to do as a politician, listing some more of his policies as Mayor of London.
He says his team did an "astonishing job" on cutting knife crime, and praises the police across the UK.
Another reporter picks up the line of questioning, noting Johnson has previously admitted to taking cocaine.
Johnson says the encounter has been brought up "many, many times" and says the country is more interested in "what we can do for them."
That's a second dodge of the drug question.