An external review into killer nurse Benjamin Geen has been launched by top NHS managers.

Thames Valley Health Authority is asking independent clinical and managerial experts to look into how the 25-year-old casualty nurse at the Horton Hospital in Banbury was able to murder two of his patients and cause serious harm to another 15.

Geen, who is now serving 17 life sentences and faces at least 30 years in prison, used a range of anaesthetic and muscle relaxant drugs to stop his victims breathing, so he could enjoy saving their lives.

Although respiratory arrest is relatively uncommon, clinical staff did not question why there had been so many cases in the accident and emergency department over a three-month period.

TVHA chief executive Nick Relph said the investigation had been agreed following discussions with the Department of Health and the Oxford Radcliffe Hospitals NHS Trust, which runs the Horton Hospital.

He added: "We're not asking for this because we think anything is systemically wrong quite the opposite. What we want to do is learn from it.

"We want to review the learning process, so we can share it across the NHS as a whole. I'm not expecting it to be a lengthy review."

Managers would like the inquiry to be completed before the end of next month when the TVHA will be dissolved to make way for the larger South Central regional SHA.

The inquiry was welcomed by Banbury MP Tony Baldry, who said: "I'm very pleased the trust has agreed to have an independent review, not least for the other staff at the Horton, because I suspect one issue that will be discovered is the phenomenal pressure at the A&E department.

"This seems a sensible way forward."