A coroner has called for a formal investigation into deaths at Wandsworth Prison after 11 men died at the category B prison last year.

Dr Fiona Wilcox was speaking at a pre-inquest hearing into the deaths of two prisoners who shared the same cell in C wing and both hanged themselves months apart.

Convicted rapist Robert Richards, 22, from Chessington, died on July 29, 2014, and left a note referring to “debts” he had inherited from his former cell mate Ian Pearson, 42, who died on March 3.

Today The Royal Courts of Justice heard this debt was £24.

Richards, a father-of-one and labourer from Chessington, died just days before he was due to be sentenced for raping and attempting to murder a pensioner in her 70s.

The woman was left in need of hospital treatment for injuries including a broken hip, vertebrae, jaw, ribs and a bleed on the brain in the violent attack in her home in October 2013.

But Dr Wilcox said an inquest into Richards’ death could not go on because of the various “themes and common issues” involved in the deaths at the 164-year-old prison – three times more than would be expected at a prison, she added.

She said: “We are at the very early stages of this inquiry. At the moment there are black holes in this investigation.”

She added the scope of the investigation should look at how complaints and concerns about bullying were handled and responded to by the prison, particularly in relation to the extortion of money and both physical and sexual assaults in custody.

A spokesman from the Howard League for Penal Reform said: “This is very worrying. We have seen an increased number of deaths in custody in recent years both in Wandsworth and other prisons and that is causing a great deal of concern.

“Not all these people would have taken their own lives, some would have died of natural causes and we also have some alleged homicides.

“There may be a number of reasons why somebody dies in custody but this rise has coincided with three factors of significant concern – the rising number of prisoners, we are at the highest we have ever been, the overcrowding in prisons is getting worse and there has been deep frontline staffing and budget cuts.”

He added the charity would be looking forward to reading an upcoming inspection report into Wandsworth Prison by HM Prison Service which is expected to be released in the next few weeks. 

A new date for another inquest hearing is yet to be set.

Dr Wilcox suggested she may visit Wandsworth Prison in the meantime.

A Prison Service spokesman said: "All deaths in custody are fully investigated by the independent Prisons and Probation Ombudsman.

"We are committed to reducing the number of self-inflicted deaths in prisons. All prisons must have procedures in place to identify and support people who are at risk of harm to themselves.”

He disputed the number of deaths at Wandsworth Prison, saying there had in fact been 10 last year - four of which were self inflicted. 

In April, Richards’ mother June Richards and step-father Andy, of Elm Road in Chessington, were both arrested on suspicion of historical rape and sexual abuse.

They have been bailed until later this month while police investigate.