"The next few weeks will be very important for the U.K. and its financial markets," Weber said. "We at UBS have always taken a worst-case scenario, and many of the regulators forced the large banks to plan on the basis of a hard Brexit. We're prepared for the worst, and we hope for the best."

Prime Minister Theresa May is trying to convince senior ministers to accept a draft European Union divorce deal that opponents say threatens both her government and the unity of the United Kingdom.

(Reporting by John Miller; Editing by Elaine Hardcastle)