The inner workings of UBS's London trading operation in the run-up to its $2.3bn unauthorised trading loss last year came back under fresh scrutiny, after UK and Swiss regulators levied a £29.7m fine on the firm.

The UK Financial Services Authority and the Swiss Financial Market Supervisory Authority said that "significant failings" in UBS's supervision, systems and controls had allowed Kweku Adoboli to cause the losses discovered in September last year.