Serco has pleaded not guilty to breaching health and safety at work laws after a guard was killed by a prisoner she was escorting.

Lawyers acting for security company told Westminster Magistrates’ Court on Monday that it denies one count of failing to ensure that staff were not exposed to risks to their health, safety and welfare.

Prosecutor Natasha Hausdorff said this failure had led to the death of custody officer Lorraine Barwell while she was on duty at Blackfriars Crown Court in June 2015.

She also said the incident was in the context of “inadequate staffing levels” and “inadequate training” and there had been a second incident at Woolwich Crown Court.

District Judge Vanessa Baraitser sent the case to Southwark Crown Court to be heard on May 17.

Following a trial of the facts at the Old Bailey in 2016, a jury found that prisoner Humphrey Burke had carried out the fatal attack on the 54-year-old grandmother.

Law degree drop-out Burke, formerly from Friars Wharf, Oxford, was ruled unfit to stand trial for Mrs Barwell’s murder as he had been diagnosed with paranoid schizophrenia.

The court heard that he had kicked her twice, once in the arm or body and then a blow to the head, causing catastrophic brain injuries.

Mrs Barwell died in hospital from a brain haemorrhage two days later.