Tunisian security forces “deliberately and unjustifiably slowed down” as a terrorist gunman massacred 30 British tourists at a popular beach resort, according to witness evidence presented at an inquest into the deaths.

Police “wasted time” before responding to the hour-long attack near Sousse in June 2015, in which 38 people were killed, the inquest heard.

The hearing at London's Royal Courts of Justice began on Monday and is set to last for seven weeks.

Counsel to the inquest Samantha Leek QC said the tourists had “needlessly lost their lives” in the mass shooting.

Presiding coroner to the inquest, Nicholas Loraine-Smith, called for those in attendance to stand to observe one minute’s silence in memory of those killed on the beach outside the Imperial Marhaba hotel, and then read out the names of all of the victims.

The attack was the deadliest on Britons since the 7 July 2005 London bombings.

From around 11.30am local time, the 38 tourists who had visited the Tunisian resort for "relaxation and enjoyment" were "systematically" gunned down, according to Ms Leek.

She cited a report compiled by Tunisian judge Lazhar Akremi, which described multiple failings by local security units. She said its contents would be examined further.

Two armed guards were in the nearby vicinity when 23-year-old Seifeddine Rezgui opened fire. He threw a grenade at one, leaving him "seemingly unconscious" and the second was unable to work his gun.

Nearby security forces "had an ability to put an end to the attack" before the police arrived, Ms Leek said, but they "deliberately and unjustifiably slowed down to delay their arrival at the hotel".

Rezgui was shot dead by police about an hour after the attack began.

The families' battle for justice has been intensified by a lengthy and truncated legal process, which had seen the Government apply for certain elements of the inquests to be kept private over concerns about national security.

During a previous hearing Andrew Ritchie QC, representing 20 families, said it was their view that a “full and fearless” investigation would be required to remain in keeping with the principle of “open justice”.