Former Barclays bank executives are reportedly set to be questioned by the Serious Fraud Office (SFO) over dealings with Qatar.Ex-chief executives Bob Diamond and John Varley, along with other former senior members of management, will be grilled by the regulator, according to the Financial Times. The move is said to be a ramp-up of the SFO's investigation into claims of corrupt arrangements with Qatar as part of the bank's emergency bailout in 2008.Barclays allegedly paid £322m in fees to investors in order to gain their support for a £5bn fundraising.A spokesman for Diamond told the BBC that the banker "will continue to assist wherever he can on anything related to Barclays, but he is unable to comment on any specific inquiry".Varley could not be reached while Barclays and the SFO declined to comment. RD