Leo McKinstry, a former aide, reveals the steely ambition and terrifying incompetence of the woman who would be leader.

The idea of Harriet Harman as Labour Leader, never mind Prime Minister, might seem laughable. As one who spent three years serving her, I shudder to think of her in charge of our national destiny. Possessed of shallow competence and intelligence, she could barely run her office, far less the country. Tellingly, in the only executive position she had ever held in Government, as Social Security Secretary between 1997 and 1999, Tony Blair got rid of her because she made such a hash of it.