A convicted serial sex offender dubbed the M25 rapist died in prison after being treated for severe heart failure, an inquest heard.

Antoni Imiela, 63, was found unconscious slumped against a table in his single D wing cell by prison officers carrying out morning checks at HMP Wakefield on March 8 last year.

CPR was conducted before category A prisoner Imiela was rushed to Pinderfields Hospital where he was pronounced dead by an A&E consultant two hours later shortly after 11am.

Imiela was given seven life sentences in 2004 for a series of rapes across the Home Counties against women and girls as young as 10.

In 2012 he was given a further 12 years sentence after being found guilty of rape, indecent assault and another serious sex offence against a 31-year-old mother-of two.

German-born Imiela was last seen by a doctor a day before his death where his medication was increased after complaining of heart problems and swollen ankles.

Imiela received a "good standard of care" at the high-security jail which was equivalent to the level he would have expected in the community, an inquest heard.

A post mortem carried out by histopathologist Mathew Alemkunnapuzha found that Imiela died on the balance of probabilities as a consequence of cirrhotic cardiomyopathy.

There was no suggestion of any suspicious circumstances or third party involvement, an inquest heard.

But a prison officer did not immediately radio a medical emergency code in line with normal procedure, however, the subsequent short delay did not play a part in Imiela's death.

Officers had initially suspected Imiela was sleeping after finding him slumped in a chair against a table in his D308 cell, an inquest heard.

Imiela had a criminal history which dated back to 1969. He was given seven life terms in 2004 for 10 serious sexual assaults.

While in prison, a cold case review took place into a 1987 attack and in 2012 he was sentenced to a further 12 years.

Imiela was born in Lubeck in what was then known as West Germany and moved to the UK aged seven in 1961.

He initially lived in Newton Aycliffe near County Durham and left school age 15 before becoming a plasterer.

Imiela then moved to Appledore on Romney Marsh where he worked on the railways.

"It seems to me that the medical care he received was every bit the standard he could have expected in the community..." - assistant coroner Oliver Longstaff

In a statement read out at the inquest, his son Aidan said Imiela had written to him in the days before his death complaining of poor treatment.

Assistant coroner Oliver Longstaff recorded a conclusion of natural causes.

He said: "At the time of his death, he was serving a number of life sentences for a number of serious crimes.

"It seems to me that the medical care he received was every bit the standard he could have expected in the community.

"In terms of the immediacy of the medical response, it could have even been quicker."

Imiela was known as the M25 rapist as many of his crimes took place near the London orbital motorway while he was living in Appledore.

His first attack dated back to 1987 when he raped a woman on Christmas Day.

The last was in 2002 when he ­indecently assaulted and attempted to rape a girl of 10 in Birmingham.

He was ­sentenced at Maidstone Crown Court in March 2004.