It was the worst fire in British post-war history as 72 lives were lost and hundreds were left traumatised by what they witnessed in the early hours of 14 June, 2017.
The Grenfell Tower blaze began on the fourth floor of the 23 floor block of flats, but spread rapidly.
It is estimated that within 17 minutes of the fire starting the building had become an inferno, leaving those inside trapped and firefighters struggling to reach them.
It also left a deep trauma in the North Kensington community where it happened. Many were left grieving loved ones while also trying to deal with the fact that they were now homeless.
Others who had not been in the tower but had witnessed the fire were left deeply affected by what they had seen.
Support counsellors sent into the community spoke of people whose homes overlooked the tower choosing to cover their windows with plastic rather than look at the charred shell of the building. The tragedy of what had happened there was simply too painful.
And the disaster left questions, a lot of questions. Primary among them was how had this happened, who was to blame and what could be done to ensure it never happens again?
In an attempt to answer those questions a government-backed inquiry was established. It was not without controversy from the start.
Many of the families affected by the fire were concerned about the make-up of the inquiry team, fearing that chairman Sir Martin Moore-Bick was too much of an establishment figure to take on the key issues they felt had to be examined. But he assured families of his desire to get to the truth of what happened, and the inquiry got under way in May 2018.
The investigation was split into two phases. Phase 1 focused on what the inquiry terms the "factual narrative" of the night of the fire, what had happened and how the tragedy unfolded. It heard from firefighters who had been on the scene as well as harrowing accounts from residents.
Now it has moved on to Phase 2, which examines the causes of the fire, including how the tower came to be in a condition that allowed the blaze to spread.
The hearings had to be suspended before Christmas because of a positive Covid-19 case among the inquiry team. This week they resume online amid the ongoing coronavirus restrictions.
This week, the focus will fall on an Irish company, some of whose executives gave evidence to the inquiry at the end of last year.
Kingspan was founded in 1965 in Kingscourt in Co Cavan and has grown to be a multi-billion euro business. It operates across the globe manufacturing insulation which is used on a variety of building types, including some for Grenfell Tower when it underwent a major refurbishment in 2012.
The key questions for Kingspan revolve around the use of insulation panels known as Kooltherm K15.
The plastic foam Kooltherm K15 had failed several full-scale fire tests, but what was being marketed for high rise buildings like Grenfell Tower on the basis of tests relating to the spread of flames across the insulation's foil surface, rather than the entire material.
The marketing also referred to an earlier test of a different, less combustible version of the insulation.
In an opening statement to the inquiry in November, Stephanie Barwise QC, a barrister representing families of those killed in the fire suggested that "even now Kingspan seeks to trivialise its wrongdoing" in relation to the provision of Kooltherm K15 for the refurbishment project.
She said that despite what the marketing suggested "manufacturers well understood the statutory regulation and guidance and sought to circumvent it by clever marketing".
As the opening statements were being made at the inquiry, Kingspan established a section on its website to deal with the inevitable questions that would arise from the evidence being heard.
It acknowledges that the "system used on Grenfell Tower was not compliant with Building Regulations, was unsafe, and should not have been used". It also adds that Kingspan had no direct involvement in the Grenfell refurbishment, and had not given any advice to those carrying out the refurbishment.
The company stated 5.2% of insulation boards used in the project were Kooltherm K15, saying it has "reviewed its testing and marketing of K15 ... and identified process shortcomings" but that it has "carried out extensive testing and re-testing ... which validates ... performance claims made previously".
The evidence given by several senior Kingspan executives to the inquiry before Christmas threw the company’s involvement with Grenfell into very sharp focus, creating headlines that saw the company share price fall by almost 12%.
Email and text communications from 2016 were read out to the hearing, which suggested some Kingspan employees described company claims on the safety of the insulation as "all lies" and talked of Kooltherm K15 being a "shit product".
An exchange between Peter Moss, a member of Kingspan’s technical team and his colleague Aaron Chalmers related to the safety performance of the Kooltherm K15 insulation. The two discussed the fact that the insulation was marketed as having a class 0 safety rating - the safest rating for the spread of flames across a surface.
But, Mr Chalmers added: "It doesn’t get a class 0 when we test the whole product tho. LOL" "WHAT. We lied?" responds Peter Moss to which Mr Chalmers replies: "Yeahhh. Tested K15 as a whole - got class 1(a worse performance). Whey. LOL."
Asked about this exchange at the hearing in December, Adrian Pargeter, Kingspan’s Director of Technical and Marketing, denied the company had lied.
Pressed by Richard Millett QC, who is lead counsel to the inquiry, Mr Pargeter was asked if he accepted "that a culture of lying about the fire safety of products is particularly serious, because you’re taking risks with people’s lives?".
Adrian Pargeter said he could not explain why the communication between the two Kingspan executives saw them describe it in the way they did.
The hearing also heard questions about the culture at Kingspan and whether that might have affected how the company responded to criticism.
Emails sent by Kingspan technical manager Philip Heath dismissed questions from a builder about its products safety by saying they could "go f**k themselves" and that contractors asking questions about the product had mistaken Mr Heath for "someone who gives a damn".
The emails were acknowledged as "totally unprofessional" by Mr Heath when he gave evidence to the inquiry.
This week the Grenfell Tower Inquiry will hear evidence from Andrew Pack, Kingspan’s global technical support manager.