The voices of some of those who suffered most in the pandemic are to be heard as the UK Covid-19 Inquiry officially begins its first day of evidence.

Two years after then-prime minister Boris Johnson announced a public inquiry would be set up, chairwoman Baroness Heather Hallett will formally open the first substantive hearing on Tuesday.

Following her statement, a video featuring people from across the UK sharing their experiences of loss will be played to those gathered at the hearing centre in west London.

As a nation, we have many lessons to learn from the pandemic and we must start to learn them now and avoid needless deaths

A statement from the inquiry team ahead of the opening warned that the film of “some of those who suffered most during the pandemic” may be “difficult to watch”.

The first module of the inquiry is expected to last around six weeks, during which there will be a focus on whether the pandemic was properly planned for and “whether the UK was adequately ready for that eventuality”.

Elkan Abrahamson, a solicitor representing the Covid-19 Bereaved Families for Justice (CBFFJ) UK group, which has almost 7,000 members, said Tuesday “marks the end of a two-year battle by the bereaved to get a statutory public inquiry”.

He said: “As a nation, we have many lessons to learn from the pandemic and we must start to learn them now and avoid needless deaths.”

The campaign group has complained of feeling marginalised after putting forward 20 people to be considered as witnesses for the first module, none of whom it said has been called to give evidence.

But a spokeswoman for the inquiry said Lady Hallett “has been clear she hasn’t ruled out calling testimony from bereaved people in later investigations, for example with the use of do not resuscitate orders”.

The spokeswoman also highlighted the Every Story Matters campaign, where people can share their experiences with the inquiry.

Tuesday’s hearing will also feature opening statements by the counsel to the inquiry and core participants, including a lawyer for the CBFFJ group.

Recent weeks have seen a row between the inquiry chairwoman and the Government over access to material.

Prime Minister Rishi Sunak has been accused of a cover-up after the Cabinet Office announced a High Court challenge to Lady Hallett’s request for Mr Johnson’s unredacted WhatsApp messages and notebooks.

The Cabinet Office said some of the information requested by the inquiry does not relate to the Government’s handling of coronavirus and is “unambiguously irrelevant”.

But the retired senior judge has refused to back down from her request for Mr Johnson’s correspondence, saying it is for her to rule what is relevant to the investigation.

Mr Sunak has denied attempting to block the probe’s access.

The inquiry is split into six modules, with public hearings scheduled to conclude by summer 2026, and interim reports published before then.

Lady Hallett is planning to publish reports for Module 1 and 2 (core UK decision-making and political governance) next year.

Module 2 of the UK-wide inquiry will look at central Government decision-making and examine issues from the perspective of Scotland, Wales and Northern Ireland.

A Scottish Covid-19 Inquiry, looking at the pandemic response in devolved areas in Scotland, is running at the same time, chaired by Lord Brailsford.