High-profile mothers including Carrie Johnson, Ellie Goulding and Olivia Colman have written to the Prime Minister calling for a national public inquiry into the 'catastrophic failure' to protect murdered toddler Preston Davey.Backing a petition so far signed by almost 100,000 people, they are among leading figures asking Sir Keir Starmer to set up a 'thorough and transparent' probe into the 'heartbreaking' series of missed opportunities to save him.Calling for urgent action, signatories including the 38-year-old wife of former PM Boris Johnson, multi-million-selling singer Ms Goulding, 39, and Oscar-winning actress Ms Colman, 52, say: 'The question that confronts us now is simple: how could this happen?'The letter is also signed by Sherwood star David Morrissey, an ambassador for domestic violence charity Refuge, and campaigner Paula Hudgell, adoptive mother of Tony Hudgell, who had both legs amputated after abuse by his birth parents as a baby.It follows an outpouring of horror since 'evil' teacher Jamie Varley, 37 – who was in the process of adopting the 13-month-old - was ordered to spend the rest of his life in jail for sexually abusing and murdering Preston.His partner, John McGowan-Fazakerley, 32, was jailed for 25 years for allowing Preston's death and participating in a sickening sexual assault on the infant. Curly-haired Preston was taken from his birth mother, herself a convicted murderer, at just five days old.'Instagram-ready' dads Varley - a former head of year at a secondary school - and his ex-public schoolboy boyfriend portrayed themselves as doting parents capable of giving Preston a second chance at their Blackpool home.Yet in the weeks before the 'happy, bubbly' toddler's death, there were a string of warning signs. Evidence in court revealed at least eight missed opportunities to save Preston Davey Jamie Varley, 37, subjected Preston to 'unremitting abuse' before murdering the 13-month-old at his home in Blackpool