Why did Boris Johnson have to sack some of his closest allies?

UK Prime Minister Boris Johnson reshuffled his cabinet last week, firing ministers who had been key supporters of his leadership. What prompted the move? London editor Denis Staunton on the eventful summer that led up to the reshuffle, what's going on in British politics right now and how Johnson is planning to win the next election. <br /><hr><p style='color:grey; font-size:0.75em;'> See <a style='color:grey;' target='_blank' rel='noopener noreferrer' href='https://acast.com/privacy'>acast.com/privacy</a> for privacy and opt-out information.</p>