There is an old article by Nick Cohen in the New Statesman which sought to explain why Tony Blair, as Prime minister, was able to behave virtually like a monarch unchecked. Cohen examined Blair's governing style, including his notoriously offhand attitude to the Cabinet, and looked at how the prerogative powers of the monarch contributed to the Prime Minister's dictatorial authority. Although the article, from 2002, clearly relates to the Blairite premiership, it is still a useful reference for AS students. The Blair precedent remains relevant in exams, and the issue of monarchical prerogative powers wielded by the PM has hardly gone away.
Cohen's article is here.