Just a quick note of clarification. What is (financial) capital? And what is money? And which part of money is cash?
'Capital' in this context means net worth - i.e. the difference between the assets of a bank and the liabilities of the bank. I appreciate this might be confusing since it is an entirely different definition than physical capital - factories and such like.
'Cash': more precisely, 'Monetary Base' or M0. Cash or deposits of the Bank of England that can be freely convertible into cash. I refer to 'monetary base' colloquially as 'cash', because that is what it is!
'Money': 'Broad money' or M3. This definition contains bank deposits as well as 'monetary base'. Bank deposits are liabilities on the banks to pay the depositor cash on demand. I refer to 'broad money' colloquially as 'money'. Tim Joslin calls deposits 'electronic money' as far as I am aware.
N.B. Banks have two requirements governing their operation: they must have enough cash and they must have enough capital in order to lend.