Two of the country’s leading prison governors could be reinvestigated after an email showed their involvement in the transfer of a vulnerable prisoner - from Streatham - who later killed himself.

Ian Mulholland, former governor at Wandsworth – the largest prison in Britain – and Nick Leader, former governor of Pentonville prison, were initially cleared of gross misconduct after it was alleged they helped try to “subvert the inspection process” by swapping self-harming and vulnerable prisoners to dupe inspectors.

The original investigation was prompted by a report from the former chief inspectors of prisons, who found five Wandsworth inmates were moved to Pentonville for the duration of an inspection, and six were moved in the opposite direction.

Managers at both prisons were disciplined after an investigation by the National Offender Management Service (Noms), which runs the prison and probation services, into the events during May and June last year.

But an email – sent from Mr Leader, who went on to be governor of the top-security Whitemoor jail, to Mr Mulholland, now head of custody in Wales – revealed the pair agreed to move another prisoner, Christopher Wardally, back to Wandsworth the day after its inspection finished.

The email forms part of a draft report into Mr Wardally’s death by the Prisons and Probations Ombudsman (PPO).

The draft PPO report, which this paper has seen, alleges major failings in his care and, through discovery of the email, links Mr Wardally’s case to the prison transfer saga – sparking calls for a Noms re-investigation.

The draft report is yet to be finalised ahead of an inquest into Mr Wardally’s death, and only a Noms investigation could consider fresh charges – which the governors could defend.

Mr Wardally, who was 25, was not initially considered to be one of the 11 prisoners involved in the prison transfer scandal, and committed suicide in HMP Wandsworth on June 12, 2009.

He suffered from several mental illnesses and previously tried to take his life at Pentonville on April 22, after which he spent a week recovering in hospital.

He was later transferred to Wandsworth, where he said he felt safer, but after a court appearance on May 26, Mr Leader accepted him back at Pentonville.

In the email to Mr Mulholland, dated May 27, Mr Leader said: “We took him back with others you kindly held during our inspection.

“The only request I have is that post your inspection if you could take Mr Wardally back.”

Mr Mulholland replied two minutes later: “Happy to take him back any time from 6 June [the day after the inspection finished].”

The PPO draft report concludes Mr Wardally’s May 26 transfer “may well have been influenced by the forthcoming inspection of Wandsworth” and recommends new evidence [in the report] be reviewed “to determine whether a renewed investigation is justified”.

It said: “The content of Mr Leader’s exchange in particular leaves the reader with the impression that the forthcoming inspection certainly influenced Mr Wardally’s movements.

“Furthermore, Mr Mulholland accepted Mr Leader’s suggestion that Mr Wardally would not be returned to Wandsworth until after the inspection ended.”

Mr Wardally’s mother, Kathleen, said the email meant two governors should now be reinvestigated.