The late Ralph Miliband wrote one of the best books about the history of the Labour Party, Parliamentary Socialism,1961.
He sometimes returned to the subject, for example in the Socialist Register 1983:
https://www.marxists.org/archive/miliband/1983/xx/advance.htm
Tom Watson has described an effort to abolish his own Deputy Leader position as going against the idea of Labour as a ‘broad church’. Harold Wilson was probably right that Labour owes more to Methodism than Marx but as Miliband notes the ‘broad’ part of the description is harder to justify historically.
Pious references to the Labour Party being a ‘broad church’ which has always incorporated many different strands of thought fail to take account of a crucial fact, namely that the ‘broad church’ of Labour only functioned effectively in the past because one side – the Right and Centre – determined the nature of the services that were to be held, and excluded or threatened with exclusion any clergy too deviant in its dissent.
A bit difficult to imagine a church broad enough to encompass slimmer-of-the-decade Watson unless one deliberately suppresses memory of half a million donated to him by Max Moseley! But this must be the limitation of my own inability to apply a forgiving attitude to the unrepentant.