A fire officer at Grenfell Tower realised “immediately” that residents should not be advised to stay put, but his concerns went unacknowledged by superiors, an inquiry has heard.

Norman Harrison, a watch manager from Wembley with 25 years’ experience, claimed he told senior managers in a “very direct and unequivocal” manner that an evacuation was needed.

Giving evidence at the inquiry into the blaze, he said his assessment was made at around 1.50am on June 14 last year, around an hour before the strategy was ditched.

The London Fire Brigade has been criticised for initially telling residents to remain in their flats despite the speed and ferocity of the inferno’s spread.

High-rise blocks should be designed so flames are contained with their flat of origin, meaning it is safer for tenants to remain inside – but this did not happen at Grenfell Tower.

Mr Harrison told a hearing at Holborn Bars on Wednesday that he approached a cluster of senior officers at a command unit vehicle and made his voice “impossible” to ignore.

However, the group, which was said to include group manager Richard Welch, offered no response “at all”, the inquiry heard.

Mr Harrison said: “I was truly shocked at such a severe fire over so many floors.

“Immediately I knew that stay-put policy should no longer apply in this building, because the stay-put policy is predicated upon the assumption that someone can stay in their flat, safe, from the one compartment that is alight somewhere in the building and they’re not going to be affected by the fire, either flames, heat or smoke.

“I could see that just didn’t apply here any more.”

His written statement described how the intensity of the fire on the external face of Grenfell Tower reminded him “of the surface of the sun”.

Mr Harrison said he knew from previous experience that each flat would be designed to withstand flames for 60 minutes – but he estimated it would take six hours to reach the top floor.

He became “extremely concerned” for both residents and colleagues, his statement said.

At this stage, 999 operators were telling occupants to stay put and await rescue.

“In reality I didn’t think that there would be an opportunity to rescue people on the upper floors and I strongly felt that the advice needed to be changed from the stay-put policy to almost a simultaneous decision to evacuate,” he wrote.

Mr Harrison said he told the group of managers that the advice given by operators “needed to be changed”.

But he did not get acknowledged by Mr Welch, the most senior officer present.

Asked by counsel to the inquiry Andrew Kinnier QC what he “took” from Mr Welch not acknowledging him, the officer said: “I knew I had impressed upon him that was my view, I knew the incident commander had a lot to consider at this incident, it was off the scale, the amount of things they had to consider.

“I knew that my opinion was at the forefront of his mind when he would come to formulate his plan. Due to the way I delivered the statement, it was impossible not to have heard it.”

He accepted during his evidence that it would have been “extremely difficult” to carry out an evacuation due to the smoke in the stairwell.

His statement explained there was only a brief timeframe when an evacuation was safe, when the fire was still only on the external face.

“I think we had a small window of opportunity to bring people down to safety, or basically as safe as it was going to be for the duration of the incident,” he said.

Mr Harrison choked back tears on Wednesday when he offered his condolences to families bereaved by the fire.

He added: “I hope you get the justice you deserve.”