A prison nurse who treated an inmate after he suffered a fatal heart attack in his cell did not realise he was seriously ill, a High Court trial has heard.

Sister Yema Gbolie, a senior nurse at HMP Wandsworth, told the court she initially believed James Best had had an asthma attack when she examined him just an hour before his death.

Mr Best, 37, of Croydon, died on September 8, 2011 while awaiting sentencing for stealing a gingerbread man from a town-centre bakery during that summer's riots.

St George's Healthcare NHS Trust and the London Ambulance Service are being sued at the Royal Courts of Justice for delays in his treatment that his family claim breached his human rights.

Their lawyers argue prison medics, employed by St George's, were too slow to call 999 when Mr Best fell ill and that this was followed by an "unreasonable delay" in LAS dispatching paramedics to the jail.

YESTERDAY: 'We are just looking for a bit of respect': Family speaks out in trial over death of Croydon riots prisoner James Best

Sister Gbolie, who was employed by St George’s and had worked at the prison for four years, was called to Mr Best’s cell at 4.19pm on the day of his death but did not summon an ambulance until 13 minutes later.

She told the court yesterday that staff in the prison's control room had not told her Mr Best's condition was critical, a claim disputed a prison officer who was working that day.

She said: "They did not tell me on the radio it was a code one [serious emergency call]. If it had been a code one it would have been a different story.

"If it was a code one I would have called for the ambulance straight away. It means they are unconscious. They are not responsive. They are probably hanging.

"If you tell me that someone has got breathing and chest pains, it may not be an emergency."

But lawyer Kirsten Sjovoll, representing Mr Best's family, said during the case’s opening on Monday: "We are talking about medically trained professionals who knew or ought to have known that this was a life-threatening situation and should have acted quicker. Seconds count and minutes matter."

She said to Sister Gbolie: "You arrived at the cell to a very distressed man crouched on the floor, unable to respond to verbal cues. Does that not suggest an ambulance should be called?"

The nurse answered: "Not at that moment, no.

"They did not tell me that it was a heart attack, they told me it was an asthma attack. We were hoping for an improvement but an improvement did not come because obviously there was something going on that we did not know at the time."

After the nurse eventually instructed the jail's control room staff to ring 999, a prison officer spent a further 13 minutes on the phone urging an LAS call handler to prioritise the call, the court heard.

Paul Morris said: "I was getting more frustrated about the situation because I believed at this point that James was seriously ill. It took a very, very long time, in my eyes, to get the ambulance."

Paramedics eventually arrived at HMP Wandsworth 30 minutes after prison medics were informed Mr Best had fallen ill.

Ms Sjovoll told the court a quicker response "might have had a real prospect of altering the outcome for Mr Best".

In tearful evidence to the court, Donna Daniel, who became Mr Best's foster mother when he was 15, said on Monday that she had taken the case to court because both trusts had refused to apologise.

She said: "We thought James deserved respect and dignity. For a decade of my life I worked as am NHS complaints manager. A lot of my work was with bereaved families and we always treated them better than we have been treated."

Owen Daniel, Mr Best's foster brother, added: "We are just looking for a bit of respect for James."

Both NHS trusts deny breaching the Human Rights Act.

The trial continues.