Citigroup is understood to have gained a lead role arranging the debt to back a £1bn (€1.5bn) bid for Travelex, the world's biggest foreign exchange company, by UK-based buy-out firm Apax Partners. A source close to the deal said Apax will sign exclusivity today.

Citigroup already has an advisory role with Apax, but sources close to the deal said today that the US bank will also lead debt funding and are understood to be putting together a syndicate to provide about £700m.