Diane Priestley was struggling to breathe and was starting to turn blue. She died of an aneurysm . An ambulance service has apologised to the family of a woman who died after errors by emergency call operators meant she was not classed as having a life-threatening condition. David Priestley called 999 three times and had to wait an hour for an ambulance to reach his wife Diane, who was struggling to breathe and whose tongue and lips had turned blue. An investigation has found that an ambulance should have been given a response priority of eight minutes to reach the 57-year-old at her home in Shildon, County Durham. Instead, a longer 30 minute response time was assigned - which North East Ambulance Service (NEAS) still failed to meet - and the grandmother-of-nine died from a ruptured abdominal aortic aneurysm on arrival at Darlington Memorial Hospital. In a letter to Mr Priestley, NEAS admitted: 'The delay in an ambulance arriving was initially due to the call handler error which resulted in an incorrect priority. 'However, as already acknowledged, we failed to attend within the timescale for the case priority that was in place. 'This was as a result of high demand on that day for emergency responses, compounded by a lack of resources to meet that demand.' Mr Priestley, 59, said he remains tormented by the thought his wife might have survived had paramedics reached her sooner on the afternoon of Saturday, September 30, last year. He described his wife of 40 years as his best friend. He added: 'It's like they say don't get bad on a weekend, as you won't get the proper treatment. 'She was my life. We did everything together.' Following the investigation into Mrs Priestley's death, NEAS found errors were made by the emergency operators during the first two 999 calls at 1.21pm and 1.47pm. David Priestley, 59, said he remains tormented by the thought his wife might have survived had paramedics reached her sooner. North East Ambulance Service admitted delay was initially due to the call-handler error . Grandmother-of-nine Mrs Priestley died from a ruptured abdominal aortic aneurysm on arrival at Darlington Memorial Hospital (pictured). Mr Priestley described his wife of 40 years as his best friend . In a letter to Mr Priestley, the North East Ambulance NHS Foundation Trust said the first operator failed to enter details about his wife's deathly colour into the system - meaning a 30 minute response priority was activated rather than eight minutes. During the next call, the second operator failed to check further about Mrs Priestley's temperature and it was not until the third 999 call at 2.13pm that an ambulance crew was assigned - eventually arriving at 2.33pm. The trust apologised and said the call handlers had received coaching on the issues identified. Mr Priestley said he felt the apology was insincere and believes the call handlers should have been dismissed. A spokesman for NEAS said: 'We would like to offer our condolences to Mr Priestley and his family, and our sincere apology for the errors made by the ambulance service.' She said a thorough investigation had been carried out and the case had been reported to the NHS commissioners as a serious incident. She added: 'Any actions resulting from a full investigation are at the discretion of NEAS and, in this case, we believe we have taken appropriate action. 'We are sorry to hear that Mr Priestley is unhappy with the outcome of the investigation. If he would like to contact his family liaison officer or our Patient Experience Team, we would be happy to go through his concerns with him.'
David Priestley called 999 three times and waited an hour for ambulance .
His wife Diane was struggling to breathe and was starting to turn blue .
Ambulance trust admitted delay due to incorrect priority by call-handler .
Mr Priestley said he is tormented by thought his wife may have survived .