Seriously surprised by the lack of knowledge out there about basic divorce law in the UK.
As I understand it, the point about a long marriage is that nobody could really disentangle all the give and take that goes on over that many years. Same with conduct- either partner could be the one to have the affair that ends the marriage, but who knows what the balance of behaviour was like over the full period of marriage? The only pragmatic way forward, if the courts aren't going to spend decades on it, is to say, right, anything over ten years counts as a "long marriage" and you are deemed to be equal partners, unless there are specific factors. Those factors, as others have said, will often work in favour of the parent who continues to have the children, not so often in favour of the partner who was wealthiest when you get married.
You remember perhaps, "all my worldly goods I thee endow?". That's a genuine commitment in law.
As for the whole "who worked hardest" thing it will vary by marriage. Not all men who go out to work are the martyrs, some of them love the work and all the status they get, and have jobs that are not all that traumatic. Equally, some women do sod-all. I have friends from Uni who have gone down the highly maintained gym bunny ladies-who-lunch route with endless staff etc. if they divorced they would get the same deal as I would, with my full time job and my three DC and all the caring and housework that I (and to be fair, also DH) do. Would that be fair, individually between us? Not really. Especially as their men have way more money than mine does. Do I resent this? No, I think it is socially important to have proper recognition of both patterns in a marriage. A few bad examples are no reason to change the system.
Not suggesting OP has done sod all- this is a response to the more general point.