Dozens of families have contacted ITV London over the treatment of their loved ones at Basildon Hospital.
The hospital is one of 14 across the country currently under investigation, because of higher than expected death rates.
The probe by the NHS Commissioning Board was ordered in the wake of failings at Stafford Hospital, where neglect and abuse led to hundreds of unnecessary deaths.
For this special report, Paul Brand spoke to two families, who claim the deaths of their relatives following treatment at Basildon Hospital could have been prevented.
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Before the final declaration on Friday, the Conservative candidate looked set to lose the City Hall race to Labour's Sadiq Khan.
The Tooting MP has been the frontrunner in the counting process ahead of Tory challenger Zac Goldsmith.
It's not just London where elections have been taking place today. There were council elections taking place across the home counties.