A preliminary report into the Grenfell Tower fire has found that the policy of urging people to "stay put" in the building had failed barely half an hour after the fire started.

The report is one of five expert reports which give new details on the cause of the inferno and why it spread so quickly.

The reports also examine the effectiveness of the fire protection measures within the building. 

Seventy-one people were killed during the tragedy in Kensington, west London, on 14 June last year.

The report carried out by Dr Barbara Lane - an expert commissioned to analyse the blaze by the public inquiry team - concluded that Grenfell Tower's only escape route was smoke logged less than an hour after the blaze started.

Dr Lane said there needs to be "serious and urgent" consideration to changing the current approach in buildings enveloped in similar material to Grenfell.

She recommends that blocks of flats have an automatic or manual means of raising an alarm sounder or providing voice alarm announcements, as currently it is not possible to easily communicate changes in advice.

The fact-finding stage of the inquiry began with an all-day address by lead counsel Richard Millett QC, following seven days of emotional family tributes to the dead.

Mr Millett said that the fundamental question which lies at the heart of the inquiry's work is "how, in London in 2017, a domestic fire developed so quickly and so catastrophically that an entire high rise block was engulfed".

He outlined the preliminary reports which are to be published today, and said they would provide a total forensic focus for the inquiry.

However, he stressed the preliminary nature of the reports, saying they can only provide provisional views at this age and that all of the experts concerned would be carefully considering evidence as it develops during this inquiry.

A provisional schedule indicates that a submission from Harley Facades, the firm which installed the cladding on Grenfell Tower, will also be read into record.

It is suspected that the cladding system installed during a recent refurbishment aided the spread of the blaze.

Throughout the week, inquiry chairman Martin Moore-Bick is to hear opening statements from a range of core participants.

This will include lawyers representing survivors and bereaved families, the Metropolitan Police, Kensington and Chelsea Council and firms involved in the block's final refit.

The hearings are taking place at Holborn Bars in central London.

The reports expected to be released today are from:

- Professor Niamh Nic Daéid, an Irish forensic scientist, who will analyse the "the cause and spread of the fire in the flat of origin and the spread of fire within and out of that compartment".

- Professor Luke Bisby, who will provide insight into "the ignition of the facade materials (including the cladding and insulation) and the fire spread over the building's external facade".

- Dr Barbara Lane, who will give evidence on "the fire protection measures within the building and preliminary conclusions on the extent to which they failed to control the spread of fire and smoke and contributed to the speed at which the fire spread".

- Professor Jose Torero, who will give findings on the spread of the fire through the building.

- Colin Todd, who will review the "different statutory and regulatory requirements in force over the lifetime of Grenfell Tower".

Additional reporting: PA