Dad weeps as he recalls how his children died in their holiday apartment

Neil Shepherd struggled against dizziness and vomiting to help his seven-year-old daughter Christianne and six-year-old son Robert as a faulty boiler leaked deadly gas into the bungalow on the Greek island of Corfu, where they were staying in October 2006.

Shortly afterwards Mr Shepherd, from Wakefield, and his partner Ruth Beatson both collapsed. They were left in hospital by the incident but survived.

Two Thomas Cook employees, Nicola Gibson and Richard Carson, went on trial in Corfu town yesterday charged with manslaughter by negligence and causing bodily harm by negligence.

They are charged alongside nine Greek nationals including staff from the Louis Corcyra Beach Hotel in Gouvia, where the family were staying, who are accused of manslaughter by negligence.

Carson, 28, and Gibson, 26, sat at the front of the court with the nine other defendants. A 12th defendant was earlier discharged from the hearing.

Giving evidence, Mr Shepherd, 38, said he and his son had a race as the family went for breakfast that morning. Robert tripped up and later said he felt dizzy, but he "brightened up" as the day went on, while daughter Christianne showed no signs of illness until later that evening.

Mr Shepherd added: "About 10 minutes after we had gone to bed Christi sat up and started being sick, " he said. "I immediately got up and went over to her to help.

"When I sat up I felt dizzy but my concern was for my daughter."

He wept as he struggled to describe how he went to get a carrier bag for his daughter to vomit into but started to feel the effects of the poisoning himself.

"When she was being sick I felt sick myself and was immediately sick. While I was tending to Christi, Ruth got up and went to sit with Bobby because we thought he would be upset.

"I can't remember anything after being sick because I passed out within a few seconds."

Mr Shepherd and Ms Beatson, who are now married, were taken to a hospital in Athens and regained consciousness after a few days. It was there that Mr Shepherd's brother told them that Christianne and Robert had died.

He told the court the family had been given no safety advice regarding gas appliances in the bungalow and did not think to ask for any as they had previously checked in the holiday brochures that all accommodation was Corgi-registered.

Mr Shepherd said he had since learned the boiler was located outside, at the back of the property on the right hand side.

"We know now that the deaths of our children was caused by carbon monoxide poisoning, " he said. "We know that there was a hole from out of the boiler into the room and we know that the carbon monoxide built up and built up and poured through the hole.".

On the stand, Ms Beatson said she did not remember anything other than going to lie with Robert when Christianne was vomiting – and then waking up in hospital.

She was asked by the court if she thought Thomas Cook was obliged to carry out safety checks on every boiler in every bungalow.

Ms Beatson answered: "I think Thomas Cook have a duty to make sure that their customers are going somewhere safe."

She was also asked about another family who had stayed in the bungalow just a few days before her and the family.

"Since we've returned to England we've found out that they were hospitalised after staying in that bungalow, " she said. "They had similar symptoms, they were dizzy and sick."

The children's mother, Sharon Wood, has also travelled to Corfu for the trial and will be called as a witness at a later date.

The trial was adjourned until February 17 and is then expected to resume on a date yet to be fixed in March.