A mother and a boyfriend she had known for only a matter of months have been found guilty of murdering her two-year-old daughter.Little Isabelle Welsh suffered a ‘campaign of violence’ at the hands of Alexandra Walker, 26, and warped paedophile Harrison Simpson, 22, who was also found guilty of sexually assaulting the young girl.In the weeks before her death in September last year, Isabelle suffered 21 broken bones before a final ‘massive head injury’ was inflicted upon her, consistent with being ‘violently shaken’ and her head ‘impacting a hard and unyielding surface such as a wall or hard floor’.When it became clear Isabelle was gravely ill, rather than call an ambulance, Walker smoked a cigarette and then used Google to search: ‘Why would my toddler be bleeding?’An hour later she called her stepfather who immediately told her to dial 999. Despite an ambulance arriving within a minute, Isabelle could not be saved.In court, Walker blamed Simpson for the injuries. Simpson declined to give evidence but his barrister claimed that it was Walker who was responsible for Isabelle's death. Teesside Crown Court heard that Walker and Simpson met on Facebook Dating in the summer of last year but within a short time he was living at her house in Thornaby, Teesside.The pair would drink and take cannabis together but Simpson began showing an unhealthy interest in Isabelle, prompting Walker to search the sex offenders’ register for his name and question whether he was a paedophile. Isabelle Welsh, two, died at her home in Thornaby, Teesside, on September 13 last yearIsabelle's mother, Alexandra Walker, has been convicted of murder at Teesside Crown CourtAlso found guilty of murder over Isabelle's killing was Harrison Simpson, 22Despite her concerns, they continued to socialise and Isabelle was left alone with Simpson on the morning of her death.When Walker surfaced from bed to care for her daughter after a night of heavy drinking, she was seriously ill.After deliberating for more than seven hours, jurors found Simpson and Walker guilty of murder and child cruelty.Simpson was also found guilty of assault by penetration of a child under 13. Walker was cleared of the same charge. The pair stood passively in the dock as the verdicts were read out.Ms Justice Norton thanked the jury for their work on such a 'difficult' case. The pair face life imprisonment when they are sentenced on Thursday. The verdicts mean jurors believed that Walker was present in the early hours of the morning, while she and Simpson had been up drinking, when the fatal blow or blows were struck to Isabelle. During the trial, they were shown video footage of Isabelle playing at home before the weeks of alleged cruelty began.In one clip she was seen charging around on the sofa at her mother's home, leaping care-free from one side to the other. When Alexandra Walker (pictured) surfaced from bed to care for her daughter after a night of heavy drinking, she was seriously ill After deliberating for more than seven hours, jurors found Harrison Simpson (pictured) and Alexandra Walker guilty of murder and child cruelty And in another clip she runs up and down the small back garden clutching a red witch's hat to her head and laughing as it falls to the ground.But within days of the second clip being filmed, Isabelle's life changed when she became the subject of prolonged abuse, injury and neglect from Simpson and Walker.The court heard there had been opportunities to save her from her tormentors, with medical professionals handing the youngster back to her mother.Just 11 days before her murder, Isabelle was reluctantly taken to hospital by her mother from the family home in Thornaby.Accident and Emergency staff at North Tees Hospital in Stockton, County Durham, did not want to allow Isabelle to leave with her mother after she was brought in with a spiral fracture to her leg, fearing potential abuse. Walker had waited two weeks to seek medical treatment despite Isabelle struggling to walk and claimed Isabelle must have hurt her leg when it got caught in her cot.But doctors on a paediatric team overruled their concerns and said there was no evidence of abuse.A health visitor was contacted because of the hospital's concern about Isabelle – but she cleared Walker on the basis of a phone call. Less than a fortnight later, on September 13, she was brought back to hospital with fatal injuries when paramedics who attended Walker's home found Isabelle lying motionless at the foot of the stairs.Prosecutor Richard Wright told the court: 'Without actually visiting Isabelle or checking on her welfare, the health visitor concluded the call and noted that she had no concerns.'Of course, she could not have known that the fractured leg was just one of numerous broken bones that Isabelle had suffered, nor that she was days away from sustaining a catastrophic and fatal head injury.'But then you may think that a telephone call to Alexandra Walker was never likely to tell her any more than Walker wanted her to know.'Isabelle had suffered 21 broken bones and internal tears from violent sexual assaults, she had 97 soft tissue injuries from fingertips where she had been tightly held and shaken and there was evidence from a pathologist to say she appeared to have been swung by a limb. Opening the case, he told the jury: 'For weeks this child had been violently assaulted and her death, by that terrible head injury, was simply the end point in that campaign of violence to which she had been subjected.'Outside court, Isabelle’s father, Josh Welsh, said justice had been done and that his daughter’s murderers deserved whole-life sentences.Asked what she meant to him, Mr Welsh said: 'My little girl… my whole life has been shattered, my whole family.'My sisters and brothers have lost their niece.'It means the world to me that we have justice for Isabelle.'An NSPCC spokesperson said: 'This is an incredibly distressing and heartbreaking case.'In the final weeks of Isabelle’s short life, she was sexually abused by Simpson and subjected to a series of violent assaults by both him and her mother, the very people who should have been protecting her from harm.'When a child dies in such devastating circumstances, people inevitably ask how such a tragedy could happen.'While Walker and Simpson are responsible for Isabelle’s death, it is vital that any potential learnings are identified and acted upon to help prevent future tragedies.'We can all play a part in keeping children safe. That means trusting our instincts, asking difficult questions and taking action when something does not feel right.'Speaking up and sharing concerns at an early stage with local authorities or the NSPCC Helpline can help ensure children and families receive the right support before a situation escalates.'The charity urged anyone with concerns about a child’s welfare or safety to call 0808 800 5000 or email help@nspcc.org.uk or - if a child is in immediate danger - dial 999.