Clearly, a would be Labour Chancellor is going to have rather different views on a just or reasonable taxation system than ourselves. But we are usually able to agree upon history. That seems not to be the case with John McDonnell:

It was under Osborne’s watch that the bank levy, introduced by the last Labour government to claw back some of the astronomical returns major banks had been making, was phased out, in his first budget after the 2015 election. 

No, that's not what happened at all. Alistair Darling imposed a tax upon bonuses. That was an idiot piece of lashing out. Osborne imposed the bank levy. This was an excellent piece of taxation.

Too big to fail banks enjoy an implicit subsidy from the rest of us. If they totter they will be rescued - that's what we mean by too big to fail, they're too big for us to allow them to fall. This is both a potential cost to us and also a subsidy to their profits for that insurance means they can borrow at finer rates. The solution is simply to charge them an insurance fee in the manner that, say, the FDIC charges banks over the pond for that guarantee upon deposits, as is also done here.

The tax was also calculated correctly. It was upon bank liabilities - what they owe to others, or, as we can also think of it, upon deposits. For a bank over a certain size, that too big thing, tot up deposits which are not already covered by various insurance schemes already being paid for. Apply a risk weighting - at sight deposits are riskier than long term bond issues for example. Charge that insurance fee.

This is, in essence, a Pigou Tax on being too big to fail.  It is excellent taxation.

Of course, Osborne, as is his wont, then messed it up, firstly by targeting the revenue yield rather than the behavioural change desired, then by getting rid of it in effect but then, you know, perhaps people who yearn to be journalists aren't quite the right choice as Chancellor.

But back to McDonnell. It's clear that we'll have differences with his plans for the economy and tax. But we really would hope that a Shadow Chancellor would know his history, especially of one of the few good taxes that have been imposed in modern times.