Further tests will be carried out concerning the deaths of two soldiers - including one who lived in London - during SAS selection training in the Brecon Beacons.
Edward John Maher and Lance Corporal Craig John Roberts collapsed on one of the hottest days of the year while climbing south Wales' highest mountain.
An inquest at Brecon Law Courts in Powys, mid Wales, gave the medical deaths of the pair as "unascertained".
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The plaque at number 16 Cowley Street in Westminster marks the brown brick Georgian townhouse where Sir John lived for 31 years.
A man reportedly armed with several knives has been arrested in Whitehall on suspicion of planning a terror attack, police have said.
Metropolitan Police officer, Tom Harrison, has been crawling the course since the race began on Sunday morning.