I have been looking at The Moorad Choudry Anthology: Past, Present and Future Principles of Banking and Finance (Amazon affiliate link, and as the title suggests, by Moorad Choudhry) as a source for my banking primer. Professor Choudhry teaches in the M.Sc.
Bank capital is the buffer on a bank’s balance sheet that allows it to absorb losses, particularly credit losses. Although there is a great deal of excitement about bank liquidity — bank runs, just like in “It’s a Wonderful Life”! — but the main danger is the capital buffer being wiped out (insolvency).