She was jailed for life with a minimum sentence of 29 years at Coventry Crown Court on December 3, after being convicted of murder by assaulting the helpless child in the hallway of her home in Cranmore Road, Solihull, on June 16 2020.

Arthur, whose body was also covered with 130 bruises, died in hospital the next day.

“Manipulator” and “calculator” Tustin was sentenced unanimously after an eight-week trial, with the boy’s “ruthless” father being convicted of his manslaughter after encouraging the murder.

Hughes’ “infatuation” with Tustin had “erased” all love for his son, sentencing judge Mark Wall QC said, and jailed the 29-year-old for 21 years.

Referring the case to the Court of Appeal, Ms Braverman said: “This is an extremely upsetting and disturbing case involving a clearly vulnerable young child.

Emma Tustin and Thomas Hughes grossly abused their position of trust and subjected an innocent child, whom they should have protected, to continued emotional and physical abuse.

“I understand how painful the public has found this case to be, but it is my job to decide whether a sentence seems unduly lenient based on the facts of the case.

“I have carefully considered the details of this case and have decided to refer the sentences to the Court of Appeal because I think they are too weak.”

The date for the hearing has not yet been set.

The grim circumstances of Arthur’s death sparked a wave of grief and rage across the UK, and led the government to announce a major review of the circumstances that led to his assassination.

It emerged at trial that Arthur was seen by social workers just two months before his death, after concerns were raised by his paternal grandmother, Joanne Hughes, but they concluded that there were “no backup problem”.

In her victim impact statement, Ms Hughes said Arthur would be “alive today” as a “happy, content and prosperous” child if her son had not met Tustin.

The high school teacher added: “It’s also clear that Arthur has been rejected by the same authorities that we as a society are made to believe are there to keep everyone safe.”

Justice Wall described the trial as “without a doubt one of the most painful and disturbing cases I have ever faced”, adding that neither Hughes nor Tustin showed remorse.

The judge said Arthur was, by the time Tustin was introduced into his life, a “happy and healthy young boy”.

But less than three months after moving in with Tustin at the start of the first nationwide lockdown, the youngster has been “shattered” by exposure to a campaign of “acute or prolonged violence,” he said.

Tustin was also convicted of two counts of child cruelty, including salt poisoning and denial of food and drink to Arthur.

She had admitted two more counts of cruelty, willfully assaulting Arthur three times and isolating him, including forcing him to stand in the hallway for up to 14 hours a day as part of a draconian punishment regime. .

Worker Hughes was also convicted of cruelty offenses which Tustin admitted but was cleared of refusing to eat and drink and poisoning his own son with salt.

Imprisoning the couple, the judge said: “This cruel and inhumane treatment of Arthur was a deliberate decision on your part to dismiss his pleas for help as meanness.”

He added that the couple’s behavior was “appalling” and that at times their actions were “mean and sadistic”.

The judge called Hughes’ “encouragement” of his partner’s actions “chilling,” including texting 18 hours before the attack saying “just put an end to him.”

He added: “You were Arthur’s father, in a position of trust, and had the primary responsibility to protect him.

“He was extremely vulnerable and you lied to his school in the last days of Arthur’s life to protect you and Mrs. Tustin.”