A "fit and well" man died after he was held for hours in a court cell on one of the hottest days of the year, an inquest jury has heard.
Rafal Sochacki, 43, was held for almost five hours at Westminster Magistrates' Court, where the air conditioning was "faulty", in June 2017.
He had just spent two-and-a-half hours in a custody van.
The jury was told Mr Sochacki was "sweating" when he was transferred from the van to the court.
He was later seen behaving "oddly" before collapsing.
The inquest at Westminster Coroners Court heard the Polish-born cleaner had been arrested by police on 19 June.
He was detained on a European Arrest Warrant at Wood Green police station, in north London, for two days where he was assessed by a healthcare worker as fit to be interviewed.
The jury heard that no concerns were raised about his health while in police custody.
At 07:20 on 21 June, Mr Sochacki was taken to court in a custody van, driven by staff from Serco, on what the coroner Dr Shirley Radcliffe described as one of the "hottest days in central London for many years".
During the journey, he asked for some water and it was noticed that the window in the part of the van in which he was held had "steamed up".
At one point he was left in the vehicle for more than 50 minutes while it was parked outside Charing Cross police station with the engine switched off.
Dr Radcliffe said when Mr Sochacki arrived at the court, at 09:51, he was seen to be sweating and some of his clothes were wet.
At about 14:00 Mr Sochacki "began to act oddly" and 45 minutes later he was "unresponsive".
'Confused and delirious'
A paramedic who attended said he thought he had suffered heat stroke.
Peter Appleby said when he arrived at the court custody block, he was told Mr Sochacki had been acting in a "confused and delirious" way before falling unconscious.
He said he had a body temperature of 39.6C (103.3F). A typical body temperature is 36.9C (98F) with anything above 38C (100F) considered "too high", the court heard.
The paramedic said Mr Sochacki's heart had stopped and he felt "hot to the touch" so he tried to cool him down with cold water and provided him with more fluids intravenously.
However, efforts to revive him failed and he was declared dead at 16:15.
The cause of death was symptoms relating to excessive body temperature linked to heart disease, the coroner said.
The inquest is expected to last for up to two weeks.