The family of a murdered mother have spoken of their fury after it was revealed that she tried to call 999 hours before she was killed but call handlers failed to alert police. Karen Catherall, 45, was viciously beaten and strangled to death by Darren Jeffreys, who she met only weeks earlier on dating site Plenty of Fish. The pair had been drinking at the pub before she returned to her home in Gwernaffield near Mold, Flintshire, North Wales, when Jeffreys, 47, followed and attacked in an alcohol-fuelled rage. Scroll down for video . Karen Catherall, 45, (right) was brutally murdered by Darren Jefferys (left) who she met on a dating site just weeks before her death. He was jailed for a minimum of 17 and a half years in February . He only called paramedics the following morning and claimed he thought Ms Catherall was sleeping, but later admitted murder and was jailed for life in February. Police have since told the family that the mother-of-two made a 999 call from her mobile just after she returned from the pub, which went through to BT to deal with. Operators at the telecommunications company connects both mobile and landline numbers with the requested emergency service and follow strict protocol. But when Ms Catherall called on September 13, last year, the call handler said they could not hear anything and therefore did not connect the call to the police or send help. Her mother, Glenys Keir, 74, and sister Lorraine Humphreys, 49, have slammed BT for not taking action at the time which they claim could have saved their sister. However, BT says its handlers acted appropriately and in line with police guidance not to pass on calls where there is 'nothing to indicate there is any problem'. Mrs Keir said: 'When we found out Karen had been murdered our whole world fell apart. 'But as we were starting to come to terms with it all, to then hear that a 999 call had been made from her mobile the night she died, it stirred up all of those emotions we had felt when we first found out Karen had been killed. Her family (mother, Glenys Keir, left, and sister, Lorraine Humphreys, right) were told by police that she had tried to make a 999 call just hours before her murder but the call was ended when operated got no response . Ms Catherall (left) had been drinking in the pub with Jeffreys (right) when he followed her home on September 13, last year. He didn't call paramedics until the following morning, claiming he thought she was asleep . 'It left us feeling sick to the stomach, devastated and fuming, knowing no one was there for Karen when she needed help. 'If they had got to her in time Karen might still be alive. She could have been here today. Now we'll always wonder if that may have been possible.' Police confirmed a 999 call was made from her mobile phone to BT  at around 7pm but it was disconnected after around 13 seconds and officers were not informed. Glenys Kier and her partner Esmor Evans leaving Mold Crown Court following the trial of their daughter's killer, Darren Jeffreys . The phone call was later enhanced by detectives, who discovered arguing could be heard in the background. Ms Catherall's family are calling on BT to review their procedures, and answer questions about the call. Mrs Keir said: 'Apparently the person who picked up believed there was silence at the end of the line. They must have assumed 999 had been dialled accidentally. 'It doesn't bear thinking about what might have happened if BT had connected the call to the police.' Ms Catherall's sister, Mrs Humphreys, a catering supervisor, added: 'You regularly hear of toddlers playing with their mum's mobile phone and ringing the emergency services by mistake. 'In those instances, the police often seem to trace the call and turn up on the doorstep. 'We want to know why that didn't happen when in this situation Karen so desperately needed their help. 'We know the police aren't to blame as they never received the call, but BT should be looking into this and reviewing their policies. 'The call might have been muffled or quiet at the other end of the line, but surely it's better to put it through to the police so they can send an officer and be safe rather than sorry. 'Who knows what the outcome might have been if they had reached her in time? We don't want any other families to lose a loved one and go through the pain we have.' A BT spokesman said: 'North Wales Police contacted BT on September 24, 2014 about whether we received an emergency call from a mobile phone number and we provided them with full details including a call recording. 'Our records show that we received the call at approximately 19.07 on September 13, 2014. 'There was no response to our operator's questioning and our operator heard nothing to indicate there was any problem before the caller ended the call after about 13 seconds. 'Police forces have requested that we do not connect such calls to them and our operator correctly followed the call handling process requested by the police.' Ms Catherall's family (pictured outside court) are calling on BT to review their procedures following the call . The 999 emergency number was set up in London in June 1937 after five women were killed in a fire. A committee discussed how telephone operators could identify emergency calls and the easy to remember 999 number was born. It was later rolled out in Glasgow and extended to all major towns and cities by 1948. Since then it has expanded massively with an average of 597,000 calls a week across the UK. BT operators answer the initial call from both landlines and mobiles and find out which emergency service is required before connecting the caller. The handler has to quickly establish whether the call is genuine before transferring them. In instances where they are met with silence they ask the caller to respond by either making a noise or coughing. This can narrow down the number of accidental or prank calls made, which account for about half of the 31 million calls made annually. Of the remaining 15.5million, 52 per cent go to police, 41 per cent to ambulance service, six per cent for fire and one per cent to the coastguard and cave and mountain rescue services. The spokesman also explained that in cases where they get no response from the caller, the operator will ask whether they can make a noise or cough. In this instance Ms Catherall apparently made no response and the phone call was terminated. Detective Inspector Mark Hughes, senior investigating officer at North Wales Police, confirmed the call. He said: 'During the early evening of September 13, 2014, a 999 call was made from the mobile phone of Karen Catherall. 'The phone call was received by the telephone company operator and managed in accordance with their policy but not directed onto North Wales Police, nor in fact any police force. 'I understand the circumstances surrounding the management of this phone call are now being reviewed by the Telephone Company following a request by Karen's family.' It was not until the early hours of the following morning, at 2.35am, that Jeffeys called emergency services, claiming that he thought she was sleeping off the alcohol and he was unable to wake her. But paramedics who arrived at the house found she had been dead for some time and there was also evidence he had tried to cover up the killing, Mold Crown Court was told. A post mortem examination revealed that her cause of death had been blunt force trauma to the head and asphyxiation. Jeffreys had denied killing his girlfriend when interviewed by police, but in December last year admitted the murder. Mr Justice Wyn Williams, hearing the case, said Jeffreys subjected Ms Catherall 'to a ferocious, sustained and in the end deadly attack'. He was sentenced to a minimum of 17 and a half years in prison.
Karen Catherall, 45, was beaten and strangled to death by Darren Jefferys . They met weeks earlier on dating site Plenty of Fish before he killed her . Police revealed the mother-of-two tried to call 999 on night of her murder . Call handler got no response and so the call was not connected to police .