Grenfell survivors have welcomed the UK prime minister’s decision to appoint two more people to oversee the public inquiry into the disaster that claimed 72 lives, after raising concerns their interests risked being overlooked.

Having initially rejected survivors’ request to widen the oversight of the inquiry, Theresa May announced on Thursday that Professor Nabeel Hamdi, an international expert in housing and planning, and Thouria Istephan, a partner at firm Foster + Partners with responsibility for construction regulations, would work alongside chairman Sir Martin Moore-Bick. The announcement comes two weeks before the two-year anniversary of the fire on 14 June 2017.

From October and following the publication of the first conclusions of the investigation into the fire, the pair will help the retired high court judge unravel the events leading up to the disaster, including the refurbishment of the tower with combustible cladding. The second phase of the inquiry which will address the preceding years will begin in early 2020. It will take place in a west London venue which has yet to be announced after participants complained that the venue for the phase one hearings in London’s legal district put the needs of lawyers above their own.

“This announcement is another step forward in our campaign for truth and justice,” the survivors and bereaved group Grenfell United said in a statement.

“We campaigned hard to secure a panel at our inquiry and thanks to support from 150,000 people across the country, today we’ve got one. We fought for this because we are certain that, at every layer, this inquiry will uncover practices that led to the deaths of our loved ones and neighbours, and continue to put lives at risk. It is important for us and for everyone in this country that this inquiry gets to the truth and delivers change, so that Grenfell never happens again.”

Hamdi describes himself as a “consultant on housing, urban development, community action planning, training, slum improvement and participatory methods”.

He worked in London as an architect on social housing projects in Stamford Hill and Adelaide Road in London. He formerly held a visiting professorship at Harvard’s graduate school of design and is a professor emeritus of housing and urban development at Oxford Brookes University.

Istephan is a partner at Foster + Partners, the architectural firm led by Lord Norman Foster, where she is in charge of the application of construction regulations in regards to health and safety.

May said she was confident the two experts “will provide the inquiry panel with the balance of skills and experience and the professional standing necessary to add real value to the inquiry’s work for phase 2”.

She said the appointments would reassure the victims, survivors, bereaved and the wider public that the inquiry “has all the breadth of skills and experience to conduct a thorough investigation”.

• This article was amended on 4 June 2019 to correct details of Nabeel Hamdi’s CV. An earlier version incorrectly said he had been educated in South Africa, and also described him as currently holding a visiting professorship at Harvard’s graduate school of design. He used to hold that position. This has been corrected.