A project manager on the Grenfell Tower refurbishment has admitted she "binned" notebooks relating to her work, after the deadly fire at the building.
Claire Williams told a public inquiry she thought the information was "documented elsewhere" and not needed.
The inquiry chairman said it was hard to understand why she had "taken it upon herself" to do such a thing.
It comes after her former colleague disclosed notebooks with "material of the utmost relevance" only last week.
The first phase of the Grenfell inquiry concluded that cladding put on during the refurbishment fuelled the fire in June 2017 in which 72 people died.
The inquiry is now examining how the blaze could have happened in the first place.
Police searched the offices of the Kensington and Chelsea Tenant Management Organisation (TMO) and took away material from the desks of staff after the blaze.
While the inquiry has access to official emails and minutes of meetings, hand-written notes could reveal more detail about decisions taken during the refurbishment of the tower.
Ms Williams told the inquiry she left the job in May 2018 and lawyers for her former employers have possession of a notebook covering "probably 2017 and 2018".
But she said she may have thrown out "two or three notebooks" containing records dating back to 2013, explaining: "If the police didn't take them, I binned them."
'Clearing my desk'
Inquiry chairman Sir Martin Moore-Bick asked: "You binned them even though you knew, by that time, there was already on foot a public inquiry?"
Ms Williams said: "I think I just tidied up the desk. I would have looked at them and thought 'There's nothing here that isn't in formal evidence'."
She told the inquiry: "There was nothing underhand about it. I was clearing my desk, I looked and decided that everything that was in there was formally represented in minutes or other paperwork and it was of little value."
She said: "It wasn't a conscious, hiding anything decision, it was 'I'm clearing my desk'. I put them in the bin."
Earlier, counsel for the inquiry, Richard Millett QC, said he would be questioning Ms William's former colleague Peter Madison on Tuesday.
He said Mr Madison, former head of assets and regeneration at the TMO, needs to give "clear and convincing explanations" of why his notebooks and diaries had not been been disclosed to the inquiry, and possibly the police, until now.
The material, including 300 pages of handwritten notes, was handed over at the weekend after Mr Madison heard the evidence of colleagues and realised they might be of value.