The French government has bowed to increasing pressure to explain how the Nice truck killer was able to get past a security checkpoint on the night of the July 14th and go on to murder 84 people.

On Thursday the French interior minster Bernard Cazeneuve called in the so-called “police of the police” to begin an independent “technical probe” into the nature of the security operation mounted by police on Bastille Day.

The minister announced that the body that investigates the French police, the Inspection Generale de la Police Nationale will be called in to scrutinize the security operation in Nice on July 14^th.

“This investigation will enable us to establish the facts around the operation while the needless debates continue,” Cazeneuve said in a statement.

The probe would be carried out for the sake of “transparency and truth that is owed to the victims and their families”.

Cazeneuve had come in for criticism after report in Liberation newspaper titled “Nice attack: security failings and a lie”, claimed he had lied about the level of security at the access to the Promenade des Anglais, the coastal road where Mohammed Lahouaiej-Bouhlel carried out his deadly 2km rampage.

Ever since last Thursday's attack the question of how in a state of emergency, with security supposedly top priority to deal with the heightened terror threat, a man could drive a 19-tonne truck onto a promenade where thousands were out celebrating France’s highly symbolic fête nationale.

“I want to know how this truck was able to enter the pedestrianized zone,” were the words of former mayor Nice Christian Estrosi on the night of the attack.

In the days after the attack PM Manuel Valls angrily rejected “shameful” suggestions that there were any security failings in Nice.

The government was forced to defend the operation on the night of July 14^th and with the ministry of interior insisting that sensitive points of security at access points to the promenade saw national police posted to reinforce the local municipal police.

“This was particularly true of the truck’s entry point, with access to the road blocked by the positing of police vehicles. The truck forced his way through the road block by mounting the pavement,” read a statement from the local authority.

After a cabinet meeting on July 16th Cazeneuve had said that police cars had been parked to make access to the promenade impossible and again insisted that the truck had got passed the road block by “violently mounting the pavement”.

But Liberation newspaper contested this version of events in their report detailing the security that was present at the entrance to the Promenade des Anglais on the night of the attack.

After studying CCTV footage and photos and speaking to witnesses the newspaper said only one municipal police car was stationed on the road at the entrance to the Promenade, but it did not block access to vehicles..

The newspaper also claimed that no officer from the national police force was present alongside two municipal officers at the security perimeter, where at around 11pm Lahouaiej-Bouhlel crashed through at the beginning of his deadly rampage.

The paper claimed national police officers were stationed further down the promenade but their two cars were also parked lengthways, meaning they did not block the route of the driver hell bent on causing death.

Following Liberation’s report Cazeneuve hit back at the “serious falsehoods in the report”.

Cazeneuve insisted the national police had secured the entry to the pedestrianized promenade by stationing two vehicles at a check point along with six officers.

“The interior ministry reiterates that the security plan set up on July 14^th was consistent is all respects with preparatory meetings held between local authorities and the police,” said Cazeneuve.

That was before he decided to launch the independent probe, which former Nice mayor Christian Estrosi will hope to answer his question of how Lahouaiej-Bouhlel and his 19 tonne truck got through.