Leaders of a school where two pupils died after a Land Rover crashed into an end-of-term tea party say they feel let down by the Metropolitan Police’s investigation.

Last week, prosecutors decided the driver of the car that killed eight-year-olds Nuria Sajjad and Selena Lau would not be prosecuted as she had suffered an epileptic seizure.

The Met has now launched a review of its investigation into the crash at The Study Preparatory School in Wimbledon, south-west London.

In their first interviews since the pupils were killed, the current and former headteacher, who was in charge at the time of the crash, have told BBC News the Met has failed to answer some of their key questions about the incident.

They say they are “angry, sad and confused” by the Crown Prosecution Service (CPS) decision not to prosecute.

Current head Sharon Maher said they had to wait nearly a year for the decision, which came just 10 days before the anniversary of the girls’ deaths.

“We were both very surprised [by the CPS decision],” Ms Maher said.

The Met said its officers had worked tirelessly through every detail of the incident to ensure a complete investigation but Ms Maher questioned that.

“It didn’t look that way to us,“ she said.

Former headteacher Helen Lowe added: “No, I think the words ‘thorough’ and ‘tireless’ suggest that you would have a body of evidence that you would be able to share… but in some areas there was just a complete lack of knowledge, of basic information.”

Ms Lowe said she was still trying to give the force the benefit of the doubt suggesting that its inability to answer questions from bereaved families, school parents and staff could be resolved.

“Maybe when they [the Met] go away and look at the evidence, they will remember the answers. But there were a number of occasions where they weren’t sure if something had been done, or they couldn’t remember.”

“At this moment in time, it would appear that I have been let down by them.”

After the CPS decision the girls’ families said in a statement that “justice has neither been done, nor has been seen to be done today”. They said they remained “unconvinced” that the investigation had been conducted thoroughly.

Speaking to BBC News, Ms Lowe vividly recalls the horror of the crash and was surprised the police didn’t interview her as a witness.

“There was terrible screaming from all the children who were terrified of course… I ran out and there was a scene of complete chaos and mayhem. The car was so big it felt like it was a big lorry,” she said.

“I immediately saw Nuria obviously very badly injured, and her mummy next to her… I just stayed with her until the ambulance came. And I just talked to her about how wonderful she was, how much we loved her and how much mummy and daddy loved her and what a special girl she was.”

She said Nuria was a talented, cheeky and very chatty girl, who was proud when her friends did well. Selena was very able and talented, who was modest and had a twinkle in her eye, she added.

In a statement the Metropolitan Police said: “Having listened to concerns from the families of both Nuria and Selena – and other parties affected – we are committed to addressing their questions, and the Specialist Crime Review Group (SCRG) will therefore be carrying out a review of the investigation.”

Last week the CPS said there was nothing to suggest the driver could have predicted or prevented the tragedy, and therefore they would not seek a criminal prosecution.

Claire Freemantle, the driver of the vehicle, expressed her “deepest sorrow” and said she had “no recollection of what took place”.

The CPS said there was no evidence she had ever suffered a similar seizure before and she had no previously diagnosed medical condition.

The school’s leadership team welcomed the Met’s decision to review the investigation but said it was clear it was willing to take further steps to challenge the police investigation.

The strain of the last year is still visible on Sharon Maher’s face. But she says the girls and staff at the school have supported each other as they try to heal.

But as they mark the anniversary this weekend Helen Lowe can’t shake one thought: “We couldn’t keep them safe on that day and I will always live with that.”