Hospital doctors failed to share with child protection services a list of "significant" injuries a five-year-old boy suffered 11 months before he was murdered, a case review has found.
Logan Mwangi had a broken arm and multiple bruises across his body when he was taken to A&E in August 2020.
But a paediatric consultant said these injuries were accidental and did not make a child protection referral.
Logan, from Bridgend, was murdered by his mother, stepfather and a teenager.
Logan's mother, Angharad Williamson, 31, is now serving at least 28 years in jail for the murder in July 2021.
His stepfather John Cole, 40, will serve at least 29 years in prison and Craig Mulligan, 14, was given a sentence of at least 15 years.
A Child Practice Review (CPR) has looked at how different agencies were involved with Logan's family in the 17 months before his death.
Cwm Taf Morgannwg health board said it welcomed the commissioning of an independent review into how it identifies and investigates non-accidental injuries.
The report said that if the injuries had been shared with social services, appropriate action could have been taken to safeguard Logan.
Jan Pickles, the independent chair of the review panel, said it was a "a significant missed opportunity".
She added: "Had further information from health been shared it most likely, though we cannot say for sure because of hindsight bias, would have triggered a child protection assessment in line with the joint agreed guidelines, as the nature of those injuries clearly met the threshold."
On 16 August 2020, Logan was taken to A&E after a fall down the stairs, which his mother described as accidental.
Thirty-one images of other 'significant injuries'
A&E made a referral to Bridgend children's services to report that there was a delay in Logan being taken to hospital after the fall.
However, while Logan was in hospital a further assessment was made and a paediatric doctor took 31 images of other "significant" injuries which included bruising to his forehead, ears, cheeks, arm and a carpet bruise on his chin.
The review said some health staff were "uncomfortable" about the decisions around Logan but felt unable to express their concerns.
It added that there was a culture in the health board where staff were reluctant to challenge decisions made by more qualified professionals.
The paediatric consultant did not consider Logan to be a child "who had sustained a non-accidental injury" and there was no evidence that information about the injuries was shared with agencies outside the health board.
Cwm Taf Morgannwg health board said it "fully accepted" the findings and said actions in progress included "strengthening a culture of professional curiosity, where colleagues are encouraged, empowered and required to report, challenge and escalate any concerns".
The review makes 10 recommendations as part of "significant core learning" to be carried out locally by the health board and local authority, and five more which need to be brought in Wales-wide.
'Complicated and complex'
This latest review, commissioned by Cwm Taf Morgannwg Safeguarding Board, praises the police for their response and also the role played by Logan's school.
It also said the initial child protection report by social services was an "accurate and concise assessment" of the risks and needs of Logan and his family, despite being a "complicated and complex task to achieve".
Logan died after Williamson, Cole and Mulligan subjected him to a "brutal and sustained" attack, leaving him with 56 injuries, including tears to his liver and bowel.
Cole and Mulligan then dumped his body in the River Ogmore, just 250m (820ft) from his home in the Sarn area of Bridgend.
Watch Logan Mwangi: A Boy Betrayed on iPlayer.
'Nothing short of horrifying'
Police officers found Logan partially submerged in the river wearing his dinosaur pyjama bottoms and a Spider-Man top.
Mrs Justice Jefford said the attack was "nothing short of horrifying".
Mulligan was not related to any of them, but Cole had raised him since he was nine months old and considered himself a father figure.
The review details the complicated background of family relationships, in which Cole and Williamson lived at points in a polyamorous relationship with another long-term partner of Cole, the mother of Mulligan.
The case is also set against the background of the Covid-19 pandemic, which had a significant impact on working practices, as well as Covid being used by the family as a barrier to engage with services.
This also led to an absence of one-to-one sessions with Logan outside the family home, partly due to restrictions and partly due to pressures from staff absence in social services due to Covid.
A social worker went to visit Craig Mulligan the day before Logan died but had no legal power to enter the home to see the younger boy.
The review's recommendations include a focus on sharing information between agencies within Cwm Taf Morgannwg's safeguarding hub and raising awareness on how the public can raise concerns about potential abuse and signs of coercive control.
It also said Logan's family circumstances had "complex dynamics", and the family courts in future should consider 12-week minimum periods to give more time for social worker assessments, when in this case they were given only four weeks.
What has been the response?
Rocio Cifuentes, the Children's Commissioner for Wales, said the report was harrowing reading, adding: "We cannot allow the death of a child to pass without us asking some fundamental questions of the system that's there to protect children in Wales, especially when a review raises recommendations we've seen before in previous reports."
She said it wasn't clear how the learning from each child practice review was used nationally to make children safe.
Tracey Holdsworth, of NSPCC Cymru, said a better joined-up system of child protection was needed.
"This review lays bare an all too familiar story of a system struggling to cope and reflects our previous concerns about the impact of Covid-19 on children's ability to seek help and the response of professionals," she said.
The British Association of Social Workers in Wales expressed its concern, adding that it acknowledged that risk assessment and management processes across social care must be co-ordinated more effectively.
The Welsh government's deputy minister for social services said lessons must be learned as she apologised to Logan's father.
Julie Morgan said: "This is a tragic case and our thoughts are with everyone affected by Logan's death, particularly his father.
"I expect all agencies involved to take time to digest this and we will work with them to take forward the other national recommendations to ensure changes are made."
Conservative social services spokesman Gareth Davies said authorities had been "quick to blame Covid" for some shortcomings in the case and questioned whether pandemic guidance had been clear enough at the time.
He said: "Not only do we see a reluctance to escalate Logan's situation in the face of obvious evidence and agencies working in silos, not sharing information, but understaffed departments that prove our concerns about high dependency of agency workers leading to cases like this are vindicated."
Plaid Cymru MS for South Wales West Sioned Williams called for an independent review of children's social work across Wales.
"Changes made now will arrive far too late for Logan, but hopefully a swift implementation of all the recommendations made in this report can help to further limit the risks to other children," she said.
Welsh Liberal Democrat leader Jane Dodds, who worked for more than 25 years as a child protection social worker, also called for a full review of social services in Wales.
"This is not about apportioning blame, but we need more staff in social work who are supported and who work together better," she added.
This latest review follows an August 2021 report that raised "serious concerns" about children's services in Bridgend.
In that report, Care Inspectorate Wales (CIW) said "urgent action" was needed but noted some improvements had been made since an inspection four months earlier.
Timeline of events leading to Logan's murder
August 16, 2020: Logan is taken to hospital by Williamson. She suspected he dislocated his shoulder when he fell down the stairs the day before. Doctors find Logan has broken arm and there is a concern about the time it took for him to be taken too hospital. Further injuries found were not referred onto child protection social services as they were not seen to be "non-accidental".
January 21, 2021: Williamson calls 101 and during the conversation tells the operator Mulligan had confessed to pushing Logan down the stairs when he fractured his arm.
March 16: Logan placed on child protection register which means social workers have to visit every 10 days.
June: Social workers in Bridgend remove Logan and his younger sibling from the child protection register as he was no longer considered to be at significant risk of harm. He was still considered to be a child in need.
July 21: Logan tests positive for Covid-19 and has to self-isolate.
July 26: Family Court approve Cole and Williamson's custody application for Mulligan, who moves in with them five days before Logan's murder.
July 29/30: Logan is seriously assaulted. The accounts of Williamson, Cole and Mulligan vary.
July 30: Mulligan's social worker Deborah Williams visits the flat but is denied entry as Logan has Covid-19. She stays for 20 minutes and leaves without seeing or hearing Logan.
July 31: CCTV shows Cole and Mulligan dumping Logan's body in the River Ogmore at 02:43.