Unicredit’s announcement last week that it had built up a 9 per cent stake in Commerzbank sparked a rare giddiness among European bank watchers. In the continent’s highly fragmented banking system, mergers are often confined to entities from the same country and lending activity is largely home-biased. Onlookers hoped the Italian bank’s move could pave the way for a deeper tie-up between Italy and Germany’s second-largest listed lenders, and kick-start consolidation across the bloc.