Calling the bottom in banking stocks is like trying to catch falling knives with one hand while scrambling eggs with the other. But, as a growing body of opinion emerges that in a few years’ time we will wonder what on earth we were thinking valuing banks so cheaply, it prompts the question as to whether last week’s bid by Santander for a small struggling UK mortgage lender is an opportunistic one-off, or whether it will open the floodgates for bargain basement banking consolidation.