Former FSA chief Sants has been on sick leave since the beginning of October, suffering from stress and exhaustion. In a statement, the bank says: "He has concluded that he will not be able to return to work in the near term. Consequently he has decided to resign from Barclays and not return from sick leave."

The departure of Kheradpir, who is moving on to fill the chief executive's seat at Juniper Networks in the US, is more of a surprise.

Kheradpir joined Barclays in January 2011 from Verizon Communications, initially as COO. In March, he was promoted to the newly created role of chief operations and technology officer, with responsibility for operational processes and systems supporting the delivery of products and services to customers as well as the bank's technology agenda.

He was credited as being a driving force in the development of Barclays' successful mobile payment app Pingit, the roll out of iPads to front line staff and the restructuring of internal staffing to bring the technical teams closer to business users in the operations department.

Barclays chief Antony Jenkins, says of his departure: "Shaygan has made a huge contribution to our innovation and technology agenda and the elements of Transform which his team are delivering have real momentum. He has infused his colleagues in operations and technology with a spirit of creative thinking and exploration which Barclays will continue to benefit from long after he has moved on."

He says the bank has begun an in internal and external search for both posts. In the meantime Allen Meyer, head of compliance, corporate and investment banking will take over Sants' post, while Darryl West, Barclays' CIO, will step into Kheradpir's vacant position, both on an interim basis.