Father-of-two William Choi lost his skies and tumbled down a steep slope A ski instructor under the influence of cannabis was responsible for the death of a top cancer surgeon surgeon who fell 750ft while on holiday with his family, an inquest has been told. Philippe Drigo agreed to put urology consultant William Choi, who had an 'inadequate introduction to off-piste skiing', in an advanced level group during a trip to the popular French alpine resort of La Plagne on March 21, 2016. Skiers were assessed on their skill in the morning before they were placed into groups, and Mr Choi was described as a good level 2 or at the beginning of level 3 - considered to be intermediate. Before lunch, the urologist asked to move into a higher group headed by Drigo so he could ski faster, and the instructor, who had the responsibility of supervising eight people, believed Mr Choi should join level 3, saying the doctor had 'underestimated' his own ability. On the first day of a planned week of skiing, father-of-two Mr Choi had enjoyed lunch with his sons, Alex and Xavier, his partner Abbey and her daughter Phoebe, before going off-piste with his group. He then lost his skis and rolled down a steep slope, hitting his head on a rock which knocked his helmet off. Mr Choi continued to hurtle to the bottom of the Losset corridor as horrified onlookers watched the harrowing incident unfold before those nearby rushed to help him as he lay motionless. Desperate efforts were made to revive the urologist, who worked at the the William Harvey Hospital in Ashford, Kent, but he died a short time later having suffered traumatic neck and spinal injuries. Drigo had denied taking drugs or alcohol when questioned by French police, but he was later found to be under the influence of cannabis, and this may have impacted his judgement, an inquest in Maidstone, Kent was told. The inquest heard Drigo was convicted of involuntary manslaughter by French prosecutors, and assistant coroner Sonia Hayes agreed that Mr Choi's death was caused by gross negligence, but it was not revealed what penalty Drigo faced. Philippe Drigo, who was under the influence of cannabis, agreed to move urology consultant William Choi to an advanced level group at the popular resort of La Plagne (pictured) In the afternoon, Mr Choi and seven others headed up the Losset corridor to the top of the 35-degree slope. Eyewitnesses told how Mr Choi had 'listened and followed instructions' given by Drigo. He started travelling down the corridor at speed but his skis were caught on an outcrop, causing him to start tumbling. His head struck a rock 'shaped like a banana', which caused him to lose his helmet from the impact and continue to plummet. By the time he stopped at the bottom of the corridor, he had fallen more than 750ft. His fatal descent down the slope was caught on camera, with the footage later handed to authorities as part of the investigation. A post-mortem revealed Mr Choi died from neck and spinal injuries known as craniocervical and thoracic trauma. French police later questioned Drigo, who denied taking drugs or alcohol.. But he was found to be under the influence of cannabis, which the inquest heard could have impacted his judgement. 'When William fell I could not do anything to avoid his fall because everything was very fast,' he said in a police interview. Evidence from investigators found the snow was hard and icy, which made it difficult to ski - despite Drigo claiming it was 'powdery'. Patrols from the resort - who were called to help an unconscious Mr Choi - later pointed out the difficulty these conditions pose to police. The inquest heard although the corridor is 'not considered extreme, it is nevertheless reserved for experienced skiers' and 'many falls' had taken place on the slope that morning. One couple, Helen and Roger Hughes, quit the group Mr Choi had been in because they felt it was 'too extreme' for them. 'In my opinion, the accident could have been avoided if the ski instructor had correctly assessed their ability,' Mrs Hughes said. Mr Hughes added: 'Philippe never asked if we were OK and if we were happy to carry on. As such I decided to leave the group and decided the site he was taking us on was too dangerous.' The inquest also heard how low cloud and poor weather conditions had impacted the ability of skiers to assess the surroundings. Mr Choi was with a group being led by an instructor in La Plagne in the French Alps A toxicology report detected no drugs or alcohol in Mr Choi's system that could have impacted his senses or judgement. There were also no defects with his equipment. Assistant coroner Ms Hayes told how Mr Choi had an 'inadequate introduction to off-piste skiing'. 'I am satisfied it would not be sufficient to say that it was simply an accident,' she concluded. 'We have heard from Mrs Hughes that this accident was avoidable. 'I am satisfied that on the expert evidence given to the French public prosecutor, they held a manslaughter charge in this case.' She agreed with the French courts that Mr Choi's death was caused by gross negligence. It was not revealed what penalty Drigo faced. Mr Choi was a highly respected doctor and the lead urology surgeon for renal cancer in the East Kent Hospitals Trust. He was vice-chairman for the Renal Cancer Service and the chairman of Laparoscopic Urological Surgery for the Kent Cancer Network. He was appointed consultant at William Harvey Hospital in Ashford and subsequently developed laparoscopic renal surgery in east Kent. He was hit by heartbreak when he lost his wife, Debbie, to breast cancer 12 years ago. After his death Mr Choi's partner Abbey described him as 'such a lovely man who would help anyone'. Speaking of the tragedy, she said: 'Bill was a very experienced skier and always wore a helmet and didn't take risks. 'We were in different groups and I just got a phone call asking me to return to the hotel because Bill had a fall. 'My first thought was that he might have broken a leg, but he died. It is devastating, particularly for the boys, whose mother Debbie died.' All rights reserved for this news site (dailymail) and under his responsibility