Paperback review: The Watchers - A Secret History of the Reign of Elizabeth I

Stephen Alford's fine study begins with an intriguing titbit of counterfactual history: in 1586, Queen Elizabeth I is assassinated, prompting a Spanish invasion after which Protestant England is reconciled to Rome.

All this might actually have come about, had Elizabeth's government not developed a surveillance state of such precision and sophistication as to make the US National Security Agency's Prism programme look amateurish. Spies were sent abroad to infiltrate the circles of political exiles; Catholic correspondence was intercepted; and plot after plot was foiled.

Alford gives us fascinating pen portraits of the key players, from the double-agent William Parry – who changed sides so often he confused even himself – to Anthony Munday, a tyro author and spy who, like an Elizabethan Ian Fleming, turned his experiences into best-selling books.