Shortcomings are still rife in child protection investigations mounted by Britain's largest police force, a watchdog report reveals.
An audit of cases found "significant weaknesses" remained apparent in Metropolitan Police inquiries involving under-18s, a year after a scathing critique exposed a catalogue of failings.
The original assessment, published in November 2016, was described as one of the most critical HM Inspectorate of Constabulary and Fire & Rescue Services (HMICFRS) has ever produced.
In a rare step Scotland Yard was subjected to a quarterly programme of follow-up inspections.
The fourth and final report in the series acknowledges the force has made progress but concludes that "consistently good" outcomes for children in the capital are still not being achieved.
Inspectors reviewed a sample of 214 child protection cases and rated 191, or 89%, as either "requiring improvement" or "inadequate".
Cases were sometimes compromised due to both poor investigations and an absence of "robust supervision", according to the report.
It said that in some areas the volume of work is contributing to "delays and drift" in child protection investigations.
In one episode cited by the inspectorate a 13-year-old girl had previously sent a picture of herself naked from the waist up to a 12-year-old boy.
The report said: "Subsequently, he threatened to distribute it more widely if she did not send more images.
"The girl rang the police but was not seen by the force for 11 days.
"The case file demonstrated extremely limited investigative action and no evidence of multi-agency work."
Examination of cases involving child sexual exploitation also revealed delays in the initial stages, while HMICFRS flagged up a "general reluctance" to seize devices, especially mobile phones from children.
The report concluded: "There are still significant weaknesses in current practices in relation to child protection which are not being effectively and consistently addressed, despite being referred back to the force for action."
HMICFRS noted that the Met has made a number of improvements including the appointment of a named lead officer for child protection and the introduction of a system for briefing officers on registered sex offenders living in their areas.
Inspector of Constabulary Matt Parr said the Met has had to make "drastic alterations" in order to make the required changes.
He said: "We found committed and dedicated officers and staff operating in an increasingly complex and demanding environment, investigating cases which are seldom straightforward.
"By and large, the force is moving in the right direction, and senior officers have demonstrated a strong commitment to protecting children.
"As a result, we found that the Met has made progress in a number of areas since our initial report in 2016, with new structures, training and oversight evident.
"However, many of these initiatives are too recent to have led to consistently improved outcomes for children.
"The force must maintain its momentum and focus on ensuring the changes it is making are leading to a better service for children in London."
The snapshot of cases examined by the inspectorate included either live or completed investigations from January to September last year.
Commander Richard Smith, head of safeguarding at the Met Police, said keeping London's children and young people safe is a "key priority" for the force.
He said: "Progress continues to be made in numerous areas despite the scale, complexity and varied multi-agency arrangements facing the Met.
"We are aware of the urgency of improving our services further, but we also know that delivering real and sustainable improvements in every aspect of our work will take time to achieve."
Action has been taken in every case where either the Met or HMICFRS identified concerns that safeguarding risks had not adequately been addressed, the officer said.
He added that the service's plans for this year have taken the inspectorate's most recent findings into account.
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