The bodies of Islander David Miller (24) and Hannah Witheridge (23) from Norfolk were discovered on the idyllic holiday island of Koh Tao on September 15 last year.
Miss Witheridge had been raped before she was killed while Mr Miller had been hit over the head before drowning in the sea.
Bar workers Zaw Lin and Wai Phyo, also known as Win Zaw Htun, initially confessed to the murders but later retracted their statements, claiming they had been tortured by police.
The long-awaited verdicts in their trial were delivered at a court on the island of Koh Samui as both men were found guilty of murder and rape and issued with the death penalty.
Mr Miller’s brother Michael, flanked by parents Ian and Sue, said outside court that the “correct decision” had been reached.
‘David was hacked down from behind, dragged into the sea, and left to die,’ he said.
‘That will live with us forever.
‘What happened to Hannah Witheridge is unspeakable.
‘We believe the result today represents justice for David and Hannah.’
Miss Witheridge’s family, who did not travel to Thailand for the verdicts, said the last year had been an “unimaginably impossible time” and they would now “digest the outcome of the trial”.
Miss Witheridge, a University of Essex student, and Mr Miller, who had just completed a civil and structural engineering degree at the University of Leeds, met on Koh Tao while staying at the same hotel.
Post-mortem examinations showed that both had suffered severe head wounds.
Prosecutors said DNA evidence collected from cigarette butts, a condom and the bodies of the victims, linked Lin and Phyo to the killings.
But lawyers representing the pair, both 22, said DNA samples from the alleged murder weapon – a garden hoe – did not match that of the two men and their confessions were a result of torture in the context of “systematic abuse” of migrants on Koh Tao.
A re-enactment of the murders in which the defendants were paraded in front of the media was also ‘staged under threat of violence’, the lawyers added.
Mr Miller’s family said the widespread interest in the case had ensured the defendants received the ‘best possible representation in court by a team of seven top lawyers’.
‘It is our opinion that the evidence against Wai Phyo and Zaw Lin is absolutely overwhelming,’ Michael Miller said.
‘They raped to satisfy their selfish desires and murdered to cover up that fact.
‘They have shown no remorse during the trial.’
The mothers of the Phyo and Lin burst into tears after the verdicts. Neither defendant showed any emotion.
British police officers visited Thailand to help with the investigation into the deaths following a direct appeal from Prime Minister David Cameron to Thailand’s military ruler, General Prayuth Chanocha.
Michael Miller said that after hearing the evidence during the trial the Thai police investigation was “not the so-called shambles it was made out to be”.
‘Like many people we initially unsure what to think when Zaw Lin and Wai Phyo were detained as suspects,’ he said.
‘We saw images of two innocent looking men surrounded by tough policemen. It was easy to conclude they might be convenient scapegoats.’
Mr Miller said the defendants’ cause had been promoted ‘vigorously’ by a group of activists including a petition handed to 10 Downing Street.
‘We believe that after a difficult start the Royal Thai police conducted a methodical and thorough investigation,’ he said.
‘We hope the campaigners who have relentlessly promoted this case will respect the process of law and the decision of the court.’
Mr Miller’s family described David as ‘irreplaceable’ and paid tribute to relatives of Miss Witheridge for the ‘horrors they are also enduring with such dignity’.
‘Our lives have been changed forever,” Michael Miller said.
‘Nothing brings David home. No last hugs. No goodbyes.
‘Our 24 years of memories and his beaming smile will always be cherished. David was intelligent, hard-working, he was caring, inclusive, enthusiastic and fun. He irreplaceable to us.
‘Our hearts will always be filled with the brightness he brought to our hearts. We are so proud of him. We and his friend will miss him terribly.’
Andy Hall, an international affairs adviser with the Migrant Worker Rights Network, which has represented the defendants, said they planned to appeal against the court’s decision.
He said: ‘The defendants have said today, whatever the decision, they accept the decision but they believe very strongly that one day the truth in this case will come out.
‘They’re confident during the appeal process they will be acquitted.’
An appeal will be lodged in the next 30 days and it could take between six months to a year before a decision is reached, Mr Hall said.
