The high court has ordered a new inquest into the death of a Windrush citizen after the original coroner failed to consider the impact of the Home Office’s “hostile environment” policy on his health.

Dexter Bristol, who was 58 when he died, moved from Grenada to the UK when he was eight in 1968. He was sacked from his cleaning job in 2017 because he had no passport, and was denied benefits because officials did not believe he was in the country legally.

He spent the last year of his life trying and failing to get the Home Office to acknowledge that he was not an illegal immigrant. Until he was sacked, he had no idea there was any problem with his immigration status.

At the inquest, assistant coroner Dr William Dolman ruled that Bristol died of natural causes after collapsing and suffering heart failure. But lawyers for Bristol’s family had obtained expert medical evidence that found stress he experienced as a result of his immigration problems was a contributing factor.

After Dolman declined to consider that evidence and refused to designate the Home Office as an interested party, Bristol’s family walked out.

His mother, Sentina D’Artagnan Bristol, issued a high court claim seeking a judicial review to quash the inquest’s conclusions.

Dolman said he would not contest the high court case, meaning that an order has been made quashing the inquest’s conclusions and ordering a new inquest in front of a different coroner.

Dolman had refused the family’s request to ask the Home Office to take part in the inquest so that the contribution of their hostile environment policies on Bristol’s death could be considered. Although he acknowledged that Bristol had been suffering from stress before his death he made no explicit mention of the last 18 months of Bristol’s life and his fear of being deported after he was told he had no right to live and work in the UK.

The legal challenge focused on three points: the coroner was accused of bias against the family’s lawyers, of failing to explore whether the death was as a result of systemic flaws in the hostile environment and of a failure under human rights legislation to investigate systemic flaws in the Home Office’s hostile environment. As well as contributing to Bristol’s death, the family say that this put other Windrush people at risk.

D’Artagnan Bristol welcomed the high court’s decision and said it must be “a full and fearless investigation” into her son’s death, looking at the effect on her son of Home Office policies which wrongly required him to prove his right to live and work in the UK.

“It was terrible what happened at the inquest into Dexter’s death,” she said. “I’m happy that the high court has quashed the decision and I hope that the new inquest will look at everything properly.”

Her lawyers have written to the senior coroner for inner north London asking for a date for the new inquest to be fixed as soon as possible.

Jacqueline McKenzie, Dexter Bristol’s immigration lawyer, said that Bristol had got into a terrible state over his dealings with the Home Office.

“We saw him deteriorating before our eyes,” she said. She made an application to the Home Office for a no time limit stamp on his passport on 29 March 2018. He died later that day unaware that his lawyer had submitted the application.

On Wednesday Bristol’s family met home secretary Sajid Javid, who told them that there were “a lot of lessons to be learned from this case”. The family is asking the Home Office to make a declaration that he had a right to live in the UK.