As for constitutions, yes, America's codified constitution is probably the oldest at 1788 containing 7,762 words. Being the oldest, makes it the most out of date. The UK's constitution is uncodified, so you have to check across multiple documents, laws, publications etc.. Parts of the UK's constitution is not written into law. The origin of the UK's constitution was in 1215, and start your research from the Peace Treaty at Lambeth 1217 if you're interested. The advantage of a constitution not being in one document, is that it's updated and flexible to a changing society.
So for example wit the US, the 2A was deemed adequate hundreds of years ago, it's now dangerously out of date (injury and death statistics indicates the truth in that)