The mother of a three-year-old boy allegedly crushed by a car seat is facing years behind bars for child cruelty.

Adrian Hoare, 23, allegedly failed to prevent her boyfriend Stephen Waterson, 25, from squashing Alfie Lamb in the footwell of his Audi convertible with his seat in February last year.

After Alfie’s death, Hoare and Waterson, the adopted son of former Tory minister Nigel Waterson, lied to police about what happened.

Following an Old Bailey trial, a jury was unable to decide whether Waterson was guilty of Alfie’s manslaughter, but found him guilty of intimidation of a witness in the case.

Hoare was cleared of manslaughter but found guilty of an alternative charge of child cruelty and common assault on another witness.

The defendants had previously pleaded guilty to conspiracy to pervert the course of justice.

Following the verdicts, Mr Justice Kerr discharged the jury and gave the prosecution seven days to decide whether to seek a retrial.

Adrian Hoare, the mother of three-year-old Alfie Lamb (Met Police/PA)

Commenting on Alfie’s case, Scotland Yard’s Detective Chief Inspector Simon Harding said: “He was a vulnerable three-and-a-half-year-old who had his life in front of him. He had no-one to care for him on that day.

“Adrian Hoare, as a mother, has the same responsibilities as any other mother who is looking after a child, especially of that age as it’s paramount she looks after their safety and their well-being. It’s clear from her actions on that day she really did not have concerns.”

On February 1 last year, the defendants had gone shopping for cushions in Sutton, accompanied by Alfie, Emilie Williams, 19, Marcus Lamb, 22, and another young child.

Alfie Lamb manslaughter court caseCCTV of Stephen Waterson and Adrian Hoare with Alfie Lamb (Met Police/PA)

Jurors were shown CCTV of Alfie running to keep up with his mother moments before he was put in the car for the journey back to Croydon, south London.

It was alleged nightclub worker Waterson became annoyed at Alfie’s crying and twice moved his front passenger seat into him as he sat at his mother’s feet.

Alfie screamed for his “mummy” but Hoare just slapped him and told him to “shut up”, said unqualified driver Mr Lamb, who was Alfie’s cousin.

Alfie LambThe Audi convertible in which Alfie was crushed (Met Police/PA)

Jurors heard the maximum space in the foot well was 30cm, and, at the touch of a button, that could be reduced to just 9.5cm.

By the time they arrived at Waterson’s home in Croydon, south London, the boy had collapsed and stopped breathing.

As medics desperately tried to revive him, Waterson left the scene and Hoare spun a web of lies, claiming she had been in a taxi.

Alfie, nicknamed “Little Tarzan” by the defendants, died from crush asphyxia three days later.

Meanwhile, Waterson gave officers a false name and false statement and sold the Audi.

Stephen Waterson (Met Police/PA)

Hoare eventually broke her silence and told her half-sister Ashleigh Jeffrey what happened in a taped conversation handed to police.

Waterson blamed Mr Lamb for being a “grass” and put his foot on his head during a violent assault in Crystal Palace Park which was filmed on his mobile phone.

Jurors were told Waterson was a controlling womaniser who used his family connections to “powerful people” to control and manipulate people.

Giving evidence, he denied he would hurt a child and said he moved his seat back once by up to an inch.

It was suggested on his behalf that Hoare must have done something to cause Alfie’s injuries.

Stephen Waterson and Adrian HoareCourt sketch of Stephen Waterson and Adrian Hoare during their trial (Elizabeth Cook/PA)

Prosecutor Duncan Atkinson QC alleged both played a part in Alfie’s death, saying Hoare “fundamentally and fatally” failed to act.

Mr Atkinson said: “When he started to cry, when he said he did not have enough room, when he coughed as if he was about to be sick, when he was screaming, when she could see he did not have enough room.

“All she needed to do was pick him up, and she didn’t, and he is dead.”

The maximum sentence for child cruelty is 10 years in prison.