The decision by UK regulators to fine but not ban Barclays chief executive Jes Staley over his attempts to unmask a whistleblower is a boost to the group's investment bank — which could yet find itself in the crosshairs of a prominent activist investor — insiders say.

Investment bankers at Barclays' Canary Wharf headquarters have expressed relief that the Financial Conduct Authority and Prudential Regulation Authority have brought to an end a joint investigation into Staley's 2016 handling of a complaint against an employee at the bank.