TUNISIAN law enforcement units deliberately delayed their arrival on the scene of the terrorist attack in Sousse in which 38 tourists were killed, an inquest has heard.

Trudy Jones, a 52-year-old carer from Blackwood was among those killed during the IS terrorist attack in Tunisia.

The hearing into the deaths of 30 Britons in the June 2015 assault by extremist Seifeddine Rezgui Yacoubi heard that a local investigation into the slaughter criticised some police for stalling as they made their way to the five-star Riu Imperial Marhaba Hotel.

Rezgui "systematically" gunned down the innocent holidaymakers on the hotel's beach before going into the grounds and the building and killing more, the hearing at the Royal Courts of Justice in London was told.

Samantha Leek QC, counsel to the inquest, said a report by Tunisian Judge Akremi had identified failings by local units which could have ended the slaughter before more police arrived and shot Rezgui dead.

She told a courtroom packed with relatives that an unnamed interior minister had told the judge some Tunisian security officers nearby had consciously slowed down their arrival.

Ms Leek said: "He said the units that should have intervened in the events deliberately and unjustifiably slowed down to delay their arrival at the hotel.

"They had the ability to put an end to the attack before the police arrived but wasted a considerable amount of time in getting to the hotel."

The hearing, scheduled to last for seven weeks, will also examine security in place at the hotel by tour firm TUI and the travel advice issued for Tunisia by the UK Government.

It followed a terror attack at the Bardo National Museum in the capital, Tunis, in March 2015 in which 24 people were killed.

Ms Leek said: "On June 26 2015, 38 tourists became the victims of a terrorist attack at the Imperial Marhaba hotel in Sousse, Tunisia.

"On that day a gunman entered the hotel from the beach, carrying an automatic weapon and a number of explosives.

"He systematically took the lives of 38 people who had travelled to Tunisia for enjoyment ... and relaxation."

Ms Leek added that an armed guard on the beach opened fire on Rezgui, who responded by throwing a grenade at him.

The guard then fell to the ground "seemingly unconscious", she added, leaving a local speedboat driver, named as AI, to pick his gun up and attempt to confront Rezgui. However he was unable to work the weapon.

She said Rezgui was thought to have acted alone on the beach - albeit with an accomplice in a van nearby - and AI brandishing the gun may have sparked reports at the time of a second gunman involved in the shooting.

The lead-up to the full inquest opening on Monday saw the Government apply for certain elements of the inquests to be kept private over concerns about national security.

An earlier hearing was told that many families feared the Foreign and Commonwealth Office (FCO) may have failed in its responsibilities to thousands of British tourists.

Some of the families of those caught in the Sousse attack said they had been assured by tour operator Thomson that it was safe to travel to Tunisia after the Bardo attack.

TUI, the travel company that owns Thomson, is represented at the inquest, as is the Government.

Ms Leek said the inquest would hear evidence "critical of TUI" as well as witnesses on behalf of the firm.

During the legal process prior to the inquest opening, the Government had applied for certain elements to be kept private over concerns about national security.

When Ms Leek referred to the possibility of asking witnesses questions that relate to "sensitive security material", Coroner Judge Nicholas Loraine-Smith said: "I am very keen to avoid any in-camera hearings."

Detective Superintendent Mark Gower, from the Metropolitan Police's counter-terrorism unit, was the first witness called.

The inquest was shown satellite images which marked out the orientation of the Imperial Marhaba Hotel in relation to other hotels.

The images are the result of 3D scans in more than 300 locations around the resort, Mr Gower told the inquest.

Photographs shown included the gate to the beach with palm trees on either side, the outdoor pool taken from a hotel balcony, and a view of the reception desk.

The court was shown a map with a moving red arrow - representing the route the gunman took.

Mr Gower said that while they could not be absolutely certain about his exact route, this was their best assessment given the evidence in Tunisia CCTV footage and from witness accounts.

A map was shown which pointed out the locations of eight CCTV cameras.

Mr Gower said a number of requests were made to Tunisian authorities for CCTV but it was only material from these cameras that was made available.

"We know there were other cameras ... whether they were genuine or dummy cameras we don't know," he said.

The inquest was shown CCTV of a white van dropping the gunman off. He gets out and walks off, carrying a large item. The van then drives off.