Video report Arena Inquiry Correspondent Amy Welch
Revelations by MI5 of what they knew about the Manchester Arena bomber before the attack are 'as staggering as they are limited' claim lawyers for the victims.
The inquiry is to hold a series of sessions with the Security Service to question 14 separate witnesses, behind closed doors, even the date has yet to be disclosed.
In previous inquests into the July 7, Westminster and London Bridge attacks, the 'gist', but not the source, of secret information was made public.
However, the Inquiry Chair, Sir John Saunders, said disclosing material in public would damage national security,
He ruled there is material 'central to the scope of the inquests', 'in particular the issue of whether the arena attack could have been prevented.'
John Cooper QC, for the victims' families, told a hearing: "The Security Service has admitted to significant fault, in both following and apprehending Salman Abedi and others but their admissions are limited"
Mr Cooper said he hoped that the inquiry was not simply 'rubber stamping' applications for secrecy by MI5.
What the families know:
A 2010 report by the Joint Terrorism Analysis Centre, based at MI5, reported the radicalisation of Libyan community in Manchester which, could be influenced by the older generation, was led by individuals with links to a group called the LIFG.
It warned the younger generation could be exposed to 'extremist viewpoints through their parents' and Mr Cooper said this 'appears to have been given an appropriate warning' for the case of Salman Abedi.
MI5's initial awareness of Abedi dated to December 30 2010, seven years before the attack, when they received a 'trace request' about him, but there was no information where that request had come from.
By July 2014, Abedi was 'clearly known to the security service' but whether or not he was 'person of interest' and to what level, was "still opaque," Mr Cooper added.
Abedi's contacts with a convicted terrorist recruiter called Abdalraouf Abdallah, including visits to him in prison in early 2015, have been reported in the press, but the inquiry heard that the Security Service is still refusing to acknowledge Abdallah by name.
In July last year the Home Secretary, Priti Patel, promised to provide the families with an indication of the number of witnesses, their roles, and a 'general indication as to the scope of their evidence.'
"A year and a month on from that we have just had the numbers and we are still waiting for the rest - that is unsatisfactory," he said.
Manchester Arena Inquiry: what the experts say on the emergency response
The inquiry heard there was 'no hope' of emergency services agreeing on how to respond to a terrorist attack and that the public would be expected to plug the care gap while they want for the ambulance service to arrive.
The Chairman of the inquiry says things 'went wrong' with the emergency response and that those responsible should expect warning letters.
The Ambulance Service - the experts view
Medical equipment could have been distributed 'more effectively' to help those injured in the Manchester Arena bombing.
An ambulance expert said items including triage packs and stretchers were "dumped" outside Victoria Station during the emergency response.
In the case of a terrorist attack the public should expect to wait 30 minutes for an Ambulance
More specialist HART trained paramedics should have been sent into the city room where the blast happened
Regular paramedics were right to be held back because they didn't have the proper training or protective clothing to enter an area that wasn't deemed safe
Stretcher which could have been used to carry the injured were dumped at the entrance to Victoria station so metal barrier had to be used instead
The public would be expected to plug the care gap while they wait for ambulances to arrive.
Figen Murray, the mother of Martyn Hett who dies says 'stop the bleed kits' should be made available to the public so that the can carry out first aid
Greater Manchester Police -the experts view
Police 'failed' in their response to the Manchester Arena attack, terrorism experts told the bombing inquiry.
They said there was no evidence of a "cohesive and co-ordinated response". GMP 'failed' to communicate and co-ordinate with other emergency services
They operated in SILO and were overwhelmed by 'operational confusion.'
'Significant omission' that GMP didn't declare a major incident for 2.5 hours
Lessons hadn't been learnt from training exercises
Some senior officers should have been sent to the scene instead of 11 ending up at GMP HQ
British Transport Police - the experts view
Experts said although there was some joint working between GMP, British Transport Police and the ambulance service within the arena foyer, the co-ordinated response by emergency services overall 'didn't work at all'.
Actions of frontline officers praised as 'exemplary'
Commander criticised for getting a taxi from Blackpool to the scene
No effective communication between BTP and other emergency services
The Fire service -the experts view
A fire service was reluctant to take risks when responding to the Manchester Arena bombing, an independent expert told the inquiry.
Various failures meant it took firefighters more than two hours to get to the scene of the 2017 attack.
Fire Crews should have gone straight to the scene instead of being sent to Philip's Park fire station 3 miles away
No suggestion that individual firefighters were "afraid to do their job" or "reluctant or resistant to take risks".
The inquiry on Tuesday will will start hearing evidence about the movements of each of the 22 victims on the night of the attack.
That evidence will focus on how they got to the concert, where they were when the blast happened, and how they were treated afterwards.
A pathologist will give evidence about the cause of death and in the cases of two of the victims -John Atkinson and the youngest victim, eight year old Saffie Rose Roussos on whether they could have survived.
For the victim's families this will be an incredibly difficult chapter of evidence to hear.