“If any big US bank were to be weak or outright fail, there could be significant contagion to the UK,” said Mayra Rodriguez Valladares, a derivatives specialist and Managing Principal at consultancy MRV Associates. “The danger is that if a US bank were to fail, UK regulators might want to ring fence a US’ subsidiary in the UK, which could exacerbate the position of the US bank and increase panic in the global banking system.”