The death of an 11-month-old girl at a Chertsey hospital was caused by a lethal overdose of phenytoin and a "a gross failure to provide basic medical care", a coroner has ruled.

Sophie Burgess was given a lethal dose — five times the required amount — of the anti-seizure drug despite a nurse protesting that it was a breach of protocol.

The baby was taken to St Peter’s Hospital in Chertsey after a seizure, for which she was given the phenytoin.

After what turned out to be a lethal dose, she vomited, went into cardiac arrest, and died three hours later.

Sophie's parents described her as “a happy baby, always smiling”.

The initial inquest into her death was halted in 2017 to allow for a police investigation, but was resumed last month without criminal proceedings being brought.

Returning a narrative conclusion at Surrey Coroner’s Court on Wednesday, with a reference that neglect was a contributory factor, assistant coroner Dr Karen Henderson said: “I’m satisfied Sophie would not have died when she did if five times the amount of phenytoin had not been administered by the nurses.

“It was a serious but simple basic error that set Sophie on a path that sadly and devastatingly led to her death.

“The inexperience of the medical staff, that lay in outdated national policy that did not meet medical standards, contributed to that journey.”

She added: “Sophie was in a dependent position, there was a gross failure to provide basic medical care.”

The nurses involved could not recall who prepared the medicine, the inquest heard, nor was the dosage checked by the consultant.

The coroner said she would write a Prevention of Future Deaths report explaining the need for medical staff to check the amount of drugs prepared before being administered, particularly when they have the ability to kill.

She also said Ashford and St Peter’s Hospitals NHS Foundation Trust had since conducted an external review and implemented all recommendations.