That seems very general - you'd have to be more specific.
Oh, dear. I hadn't intended to write a dry screed of text on those points, derailing the thread and boring other posters. There was a lot of that in the wake of the death of Elizabeth II.
An historian is not the same thing as a Constitutional Historian. Nor is a historian necessarily a Constitutional expert, let alone a leading one.
I'm sure most people are aware that within every broad academic discipline there are area specialists. That hardly needs pointing out. As for recognized experts in particular fields, wherever there's an intellectual question there is contestation, usually emanating from numerous different angles. This constatation will also take into account the particular ethical, political or theoretical biases conveyed through any of that person's research. Otherwise there would be no scholarly discussion. No self-respecting academic would ever accept a particular point merely because it was expressed by the eminent Professor Snodbury of Footlights College, Oxbridge.
The term 'constitution' is ambiguous. F.W. Hegel, no less, was one of the names suggesting it was founded on a series of abstractions, and that no country had managed to produce a clear one yet. de Tocqueville, writing shortly after Hegel, did so in words to the effect that the British constitution was subject to continual shift, and didn't in reality exist (forgive the lack of actual quotes and a cogent system of citation, won't you. I don't have the time).
Crossman, around the 1960s, reckoned cabinet government had been replaced by prime ministerial government (aka presidential). And that leads to the sideways point that the system of government we have now is something very close to republican; along the model of Plato's democracy. We could ditch the Windsors tomorrow and replace them with absolutely nothing, not that this is the solution I happen to think is needed.
The thing that throws a lot of this into stark relief is the very draconian, authoritarian Blair government. They come into power in 1997, and almost immediately bring in the most radical constitutional reforms seen since the First World War. HR Act reform, FOI Act, reform, Devolution of Scotland, N.I., and Wales, and something passing for Reform of the Lords. And this throws up additional, very significant questions. There's a much more recent study by Bogdanor, claiming that through these actions the old constitution was pretty much usurped and superseded with a new one.
In sum. the meaning of 'constitution' is ambiguous. There's a lot of arguing over what it actually is, and IF it actually is. It's not me, BTW, saying the British don't possess a constitution. I'm merely pointing out that a number of people have done so. We have a set of conventions and institutions regulating the process of government: by that definition, we have a constitution. To say that, at least, it's nebulous, subject to a great deal of debate, and difficult for most people to pin down, is a reasonable suggestion.
It doesn't appear to me you've given much thought to what kind of written constitution you wish to see either or much of an idea how to get there in terms of obstacles in the road.....
With respect, I'm neither a politician nor Mystic Meg. I could link you to any decipherable constitution with a clear meaning, such as that of the Republic of Ireland, but it's not for me to write a new UK constitution. I'm suggesting that these are huge questions and that now is a good time for discussion of these issues. It's a long process, and when/if it happens will likely span many years.
The British way is evolution, not revolution.