The Grenfell Tower Inquiry has heard that a Kingspan executive agreed with the suggestion that fire test reports had been "almost kept secret".
Andrew Pack, who appeared via videolink from Dubai, is a global technical support manager reporting to the Middle East division of the Irish company.
Mr Pack was questioned on a number of issues surrounding the use of Kooltherm K15 insulation in a refurbishment of the Grenfell Tower in 2012.
Mr Pack said his involvement with K15 was small and that it had been one product in "a basket of products with which he dealt".
He began working for Kingspan in 1992 as a technical support manager, dealing with queries from contractors and architects about the suitability of Kingspan insulation for a variety of building projects.
Asking about the process used to test the company's product, counsel for the inquiry Ms Rachel Troup asked if it was the case that in the past fire test reports were "almost kept secret".
"Yes. Correct," Mr Pack replied, saying that it was information which tended to be kept among those who had carried out the tests.
Questioning of Mr Pack by Ms Troup centred on certification from the Local Authority Building Control which classified Kingspan's K15 insulation as "a material of limited combustibility".
That classification reached the minimum standard for use on high rise buildings.
Mr Pack was asked about an email sent by his line manager Philip Heath on 7 May 2009, relating to the LABC.
Mr Heath said in the email (which was not sent directly to Mr Pack) that "we can be very convincing when we need to be. We threw every bit of fire test data we could at him, we probably blocked his server. In the end I think the LABC convinced themselves Kooltherm is the best thing since sliced bread."
Mr Pack described the email as nonsense, saying he totally disagreed with it.
Kingspan says the Grenfell Inquiry has highlighted "historic process shortcomings and unacceptable conduct within a part of our UK insulation business, for which we apologise unreservedly."
It has also said that it was not directly involved in the Grenfell refurbishment project in 2012, and provided no advice to those working on the project, which used 5.2% of the company's product.
The company says its testing and retesting of K15 mean it is confident that the systems incorporating current K15 insulation "can continue to be used safely, if used in compliance with the relevant building regulations".
The Grenfell Tower Inquiry hearings moved online having been suspended before Christmas because of a positive Covid-19 result among the team involved in the hearings.
Opening this morning's hearing, Chairman Martin Moore-Bick acknowledged that the inquiry will continue in a very different form as a result of coronavirus restrictions.
He said that even limited attendance at the inquiry would have imposed a risk on essential staff and witnesses, some of whom would have had to travel a considerable distance.
As a result the hearing is now online with witnesses and counsel appearing remotely.