Power and the Palace will examine how the relationship between the sovereign and the country's political leadership has changed over the last 200 years. It will show how even in relatively recent history - the first half of the twentieth century - sovereigns were involved in politics in ways that would be regarded as totally unacceptable now. The stock phrase used by palace advisers today is that the sovereign is 'above politics'. And yet the fascinating thing is that has changed without there ever being any change to the constitution: which, of course, there can't be, because Britain doesn't have a written constitution.

Two main threads run through the book. One is how the monarchy gradually ceded political power over the last couple of centuries, culminating in the 2010 Cabinet Office manual, drawn up under Gordon Brown with the assistance of Buckingham Palace, which was basically designed to keep the sovereign out of the decision-making process in the event of a hung Parliament. The other is how the monarchy has fought tooth and nail to make sure its finances have remained secure, from the way it talked the government into allowing the sovereign not to pay income tax for most of the twentieth century to the way it landed a spectacularly good deal for the financing of the royal family under David Cameron in the form of the Sovereign Grant. Successive governments have made sure that the royal wealth remains protected. These two threads share a common theme: they are about ensuring the long-term survival of the monarchy, by keeping the monarchy solvent, but also above criticism.

Based on the author's high-level access to both the Palace and 10 Downing Street, the book is full of revelations that will rewrite our understanding of the relationship between the monarchy and the government.