UBS chair Colm Kelleher was driving back to Zurich from Bern in March 2023 when his phone rang. The Irish banker was heading home after a weekend of tumultuous negotiations that had culminated in a historic $3.25 billion (CHF2.55 billlion) deal to rescue UBS’s rival Credit Suisse. On the other end of the line was Jamie Dimon, chief executive of US giant JPMorgan Chase and a veteran of emergency bank takeovers, calling to offer a piece of advice, even as he thanked Kelleher for his contribution in stabilising the global banking system. Dimon — whom Kelleher knew well from his years atop Wall Street rival Morgan Stanley — had a clear message, according to people briefed on the conversation: do not let the Swiss authorities change the terms of the deal to acquire UBS’s traditional adversary. More than three years later, UBS and the Swiss government remain locked in a stand-off over how much capital it must have to guard against disaster, a dispute that stems from the deal struck on …