The manual is hardly a subject to pump adrenalin. Yet its very obscurity holds the key to its significance. In setting out a summary of existing constitutional practices, it arguably infiltrates a change in the conventions concerning the resignation of the Prime Minister which, if accepted, will lead Britain further to abandon the Westminster model in favour of a Continental European one. Even in its preliminary form, the Cabinet Manual arguably influenced the structure of negotiations between the political parties after the 2010 general elections and helped the Liberal Democrats achieve their key aim: the AV referendum.

My case is that the manual is a significant feature of an accumulation of reforms which are destroying the British constitution.

In countries where the fundamental rules of politics are contained in a single constitutional document, it frequently falls to judges to decide whether laws enacted by the legislature or actions of the executive conform to the constitution. Constitutions thus give authority to judges, who themselves are unelected and who may be unaccountable. Traditionally, the UK has limited the role of the judiciary over fundamental political matters. The system of parliamentary sovereignty is fundamental to the British political order. Constitutional measures have the status of ordinary laws which may be amended or abolished by a bare majority in each chamber of Parliament.

Thus, the monumental decision taken by the House of Commons in 1972 that the UK should become a member of the European Economic Community (subsequently the European Union) was taken by a threadbare majority. The referendum that followed too was decided by simple majority.

The achilles heel of the traditional UK constitution is that it contains no inbuilt protection against casual, surreptitious reform.