The group set up to study previously secret documents relating to the Hillsborough tragedy saw for themselves on Tuesday the scale of the archive they are set to examine.
The Hillsborough Independent Panel is overseeing the public disclosure of archives held by the emergency services, the city council and other public bodies in Sheffield.
The documents relate to the disaster in April 1989 when 96 Liverpool fans died in a crush at Hillsborough Stadium after going to see their team play Nottingham Forest in an FA Cup semi-final.
The panel, chaired by the Bishop of Liverpool, the Rt Rev James Jones, was set up last year after the 20th anniversary of the tragedy.
The group visited the archives in Sheffield to look at where the documents are being held and to talk to staff involved in the project.
The bishop said the archive of around 600 boxes of material was "daunting" in its size but he praised the work which has already been done to bring it together and organise it.
The seven members are broadcaster Peter Sissons; public information expert Christine Gifford; TV producer and researcher Katy Jones; Paul Leighton, former deputy chief constable of the Police Service of Northern Ireland; academic criminologist Professor Phil Scraton; Bill Kirkup, former associate medical director at the Department of Health; and archivist Sarah Tyacke.
After his initial look at the documents, the bishop said: "The reason we're doing this is because this is the principal purpose of the panel, which is to oversee the maximum possible disclosure of the documents which are contained in the Sheffield archive.
"This today was our first opportunity of walking through the archive and seeing the shelves of material."
He said: "It's a very large archive.
"I'm very impressed by the way the archive has been kept.
"This is a three-star archive which speaks of the excellence of the service here."
He added: "It is daunting and that's when you realise you need a team. There's no one person that can do this."
The panel convened for the first time in Liverpool earlier this month when it met representatives of Hillsborough victims' families.
The bishop said the panel's tasks were to ensure the maximum public disclosure of the documents and to write a report detailing their contents.
The group will complete the task by making recommendations about a national archive of the Hillsborough documents.
The bishop has said they would "leave no stone unturned" in their search for the truth, which included holding meetings with South Yorkshire Police.
Lord Justice Taylor's inquiry into the disaster, which reported in 1990, criticised senior police officers on duty at the match for a "failure of control" and recommended the introduction of all-seater stadiums.
But the families have continued to call for further inquiries into the deaths.
The bishop said today: "We've got two years in which to do this work.
"The next time we meet will be to establish the protocol of how we will actually access this material.
"Today has enabled us to get some sense of the size of the operation and to meet some key staff."
Some people have estimated the number of documents in the Hillsborough archive could total around two million.
Later, the panel visited South Yorkshire Police HQ where it met with chief constable Meredydd Hughes and other senior officers.
The bishop said the meeting had been very useful and he believed the families of those who died could be reassured the force was giving its full co-operation to the process.
He said: "The panel was greatly encouraged by the initiative the chief constable has already taken in depositing his whole archive with the Sheffield archive."
The bishop added: "I think the people of Sheffield, as well as people in Liverpool and people in Nottingham, can be assured the chief constable has given his word he will co-operate fully with the purpose of the panel which is the maximum possible public disclosure of the documents in the Sheffield archive."
The bishop said the day in Sheffield had been very productive, especially in terms of forging relationships between the various people who have co-operated to put the archive together. He said the good relationship between the group and South Yorkshire Police was clearly very important.
The panel will meet again next month, he said.
Mr. Hughes said: "It was encouraging to meet the Hillsborough Independent Panel here in Sheffield. The members were keen to ensure that it is well understood by all that they are not a new inquiry into the disaster.
"I was pleased to have the opportunity to brief them on the work already carried out by South Yorkshire Police and our local partners.
"Since March last year we have all been steadily bringing together our remaining files and documents to ensure the archives here in Sheffield are as complete as possible.
"The establishment of the panel, the recruitment of the archivists and the growing recognition of the scale of this undertaking, both locally and nationally, means that interested parties and the public generally are gaining an insight as to just how long this process will take.
"We will create a public archive of documents for the historians of the future as well as the stakeholders of today - all of whom will be able to judge the events of Hillsborough for themselves."