the brits dont even have one!

they'll tell you that they do have one, but they just... prefer not to write it down:

The constitution of the United Kingdom comprises the written and unwritten arrangements that establish the United Kingdom of Great Britain and Northern Ireland as a political body. Unlike in most countries, no official attempt has been made to codify such arrangements into a single document, thus it is known as an uncodified constitution.

they're quite committed to the bit, even going so far as having a whole thing they call "UK constitutional law" (replete with varieties of court dress).