A British tourist, whom is understood to be a friend of victim David Miller, is being questioned by police in Bangkok over the brutal murder of Miller and Hannah Witheridge.

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The unnamed man was on the island at the time of the attacks but left shortly afterwards, boarding the first ferry to leave Koh Tao.

Thai Police have said that the man has not yet been arrested, but will be questioned further in the next 23 hours.

He has also agreed not to leave the country while murder inquiries continue.

A second man in Mr Miller’s group was also detained after he was found with injuries to his hands, but he was released after providing what police described as a ‘satisfactory explanation’.

Police chief Colonel Prachum Ruangthong told the Mirror he saw “jealousy” as key to solving the crime.

He said: “Why, why, why were they hit so hard?

“It was bad, very bad.”

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Police have said that the pair sustained horrific injuries, with deep wounds to their heads and face.

A bloodstained hoe, believed to be the murder weapon, was found close to their semi-naked bodies.

Miss Witheridge’s body has been sent for forensic tests amid fears she could have been raped during the attack.

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As police continue to question migrant workers and tourists on the island, the families of both victims have paid tribute to them.

Miss Witheridge was described by her family as "a beautiful, intelligent, loving young woman who poured joy into the lives of all who knew her", while Mr Miller was a "hard-working, bright and conscientious" young man who would be "sorely, sorely missed".