Constitutionalism is based around the idea of having a legal system of two layers - ordinary day to day law, and a deeper more profound law that somehow matters more and should be harder to change.

The US pioneered the idea of having a constitution from which the branches of government derives their power and that sets the rules of the game.

In the UK, all laws are technically of equal value, and the system instead relies heavily on tradition and obscure institutions like the monarchy and house of lords. They don’t have a constitution, though of course they have laws that constitutes the law of the land. It’s not necessarily a bad thing - if laws existed for hundreds of years, it might be because they do some good or at least limited harm.

German constitutionalism is largely built around the ideas of Kelsen, and is very much a system of constitutionalism. That they opted for the word Grundgesetz instead of Verfassung for the legal text is of course interesting, but who interprets this text other than the BundesVERFASSUNGSgericht? It’s a constitution, they just named it the basic law. Reflecting precisely this two-level system of laws that constitutionalism is designed around, and that the UK lacks.

What should and should not go into constitutions is an ongoing debate of course, but I haven’t heard anyone argue for provisions about sparkling wine. Sadly.