But the Tory politicians turned super-heroes after they rushed to the aid of a woman who collapsed in the street.
The Prime Minister and the London Mayor got out of their official car after spotting her fall to the ground as they drove through north-west London to an election campaign event.
A passing GP first tended to the woman followed by a paramedic and ambulance summoned by the PM's security detail.
Downing Street would not confirm an eyewitness claim that the Prime Minister held the woman's hand until help arrived.
Paramedic Dominic Stark, who was at the scene, said: "The Prime Minister and Boris Johnson pulled over when they noticed a woman collapse on the street. When I arrived a few minutes later, I found the PM holding the woman's hand.
"I took over caring for the patient and they left a few minutes later."
A London Ambulance Service spokesman said the woman was taken to hospital and was "OK".