Metropolitan Police investigators said new information about Gareth Williams, who died in 2010, had come to light.
The body of Mr Williams, from Anglesey, was discovered at his Pimlico flat, and a coroner later concluded he was unlawfully killed.
A year later, in 2013, the Met concluded the 31-year-old had died as a result of an accident.
At the 2012 inquest into Mr Williams' death, coroner Fiona Wilcox reached her conclusion based "on the balance of probabilities".
"[However] most of the fundamental questions in relation to how Gareth died remain unanswered," she said.'