You asked

What is the net-worth of all commercial banks operating in Britain? Please provide historic data to present.

We said

Thank you for your enquiry. The data you require is published as part of the National Accounts Blue Book publication for Financial Corporations, Table 4.2.9:

https://www.ons.gov.uk/file?uri=/economy/grossdomesticproductgdp/compendium/unitedkingdomnationalaccountsthebluebook/2016edition/unitedkingdomnationalaccountsthebluebook2015edition/bbchapter04fcsector1.xls

Please find the latest data including historic series from 1987 in the table attached.