British officials had worked for months trying to track down the captured men as rumours floated that they had been taken out of the country.
Nigerian government sources said that the men were killed before the arrival of security forces.
The wife of one of the guards holding the hostages in Nigeria claimed they were taken into a toilet and shot dead during the failed rescue attempt.
Today's hearing will take place at Wiltshire and Swindon Coroner's Court in Salisbury.
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The bill is President Trump's first attempt at passing a big legislative piece through Congress.
Settled and sunny for most tomorrow, a little more cloudy on Sunday.
Residents from a town in East Sussex where the Westminster attacker once lived have described him as "intimidating" and "unpleasant".