It would be a mistake to imagine that the US constitution is confined to The Constitution. Caselaw is important - and there are conventions which do control the behaviour of the political actors.
It is worth comparing the constitutions. What can we learn from each? What are the advantages and disadvantages of each system? How far are constitutional practices transferable?
Separation of powers has always been an aspect of the British system (Montesquieu used the British system as an example of separation of powers!). However it has always been limited. One of the most important developments of recent years has been a strengthening of the separation in the UK. The Lord Chancellor once played an active role in the highest Court (House of Lords judicial Committee), sitting as a judge - while - like all of the Judicial committee - being a member of the legislature (House of Lords). He was also a leading member of the Cabinet, a key body in the Executive. No longer - the Lord Chancellor has no role as a judge. The Supreme Court has been created, and the link to the House of Lords broken.
But has it gone far enough. Some argue, for example Graham Allen MP, that we need to move from a parliamentary system - to a complete separation of the Executive and Legislature.
What do you think? What lessons can be learned from your own system? Do share your views on Washminster.