The 23-story tower, owned by the wealthy west London borough of Kensington and Chelsea, was destroyed on the night of June 14, 2017, in Britain's worst fire in a residential building since World War Two.
The disaster shocked the nation, prompting an outpouring of grief as well as soul-searching over allegations by survivors that neglect of their ethnically mixed, largely low-income community had played a part.
In its first phase, now complete, the public inquiry led by retired judge Martin Moore-Bick examined in forensic detail the sequence of events on the night of the blaze.
The second phase will look into events in the years leading up to the fire, in particular a recent refurbishment during which flammable cladding was fitted to the external walls, the key factor in the rapid spread of the fire.
Witnesses who will give evidence in the phase two public hearings will include representatives from the architects, contractors and sub-contractors who carried out the refurbishment, and from the makers and sellers of the cladding.
In a statement introducing phase two, the inquiry's lead counsel Richard Millett said that out of all the bodies involved in the refurbishment, only the Kensington and Chelsea local authority, which commissioned it, had admitted any failings.
In written statements submitted by their lawyers, the companies involved had refused to admit any mistakes or sub-standard work, Millett said, describing their attitude as "a merry-go-round of buck-passing."
"One finds in these detailed and carefully crafted statements no trace of any acceptance of any responsibility for what happened at Grenfell Tower," he said.
The main contractor in charge of the refurbishment was privately owned British firm Rydon. The cladding supplier was the U.S. firm Arconic Inc, while the makers of the insulation material used as part of the cladding system were Celotex Corp, a U.S. subsidiary of France's Saint-Gobain .
London's Metropolitan Police, who are conducting their own investigation into the fire, have said they were considering possible criminal charges including gross negligence manslaughter, corporate manslaughter and breaches of the Health and Safety Act.
But the police have said they would not announce any decisions on charges until the public inquiry had concluded, because they needed to take into account its findings.Phase one of the inquiry, now complete, established that the fire had started in a fourth-floor flat due to a faulty refrigerator, before breaking out to the external cladding and engulfing the tower, re-entering the building via the windows.