The Grenfell Tower inquiry is hearing closing statements from lawyers representing the survivors, the bereaved and organisations involved with the response to the fire.
Stephen Walsh QC, representing the London Fire Brigade was the first to speak.
Officers who gave evidence at the inquiry's first phase found it "extremely challenging, and in many cases particularly harrowing" to re-live their role, he said.
He said it was a "stark fact" that one of the biggest fire services in the world had been "severely challenged, in some elements overwhelmed" by what happened on the night of June 14 last year.
Addressing chairman Sir Martin Moore-Bick, Mr Walsh said:
Mr Walsh said there were issues the inquiry's expert witnesses did not agree on and that these needed further examination in the second phase of the inquiry.
This is not expected to get under way until April or May 2019, and will look at the wider issues surrounding the fire.
Critical findings of the chairman, he argued, with the exception of any urgent recommendations he may see fit to suggest, "can only properly be made when the full context is examined in phase two".
Sir Martin is due to produce an interim report after the first phase, which is drawing to a close, has finished.