Growing concern over the handling of the murders of two British tourists - including Norfolk's Hannah Witheridge - have left huge question marks over hanging over the case against the two suspects who were said to have confessed to the killings.

Under-fire Thai police have been forced to defend their actions amid allegations the two Burmese men charged with the killings were tortured, claims which have prompted action both at home and abroad.

Earlier this week a Thai diplomat was summoned to the Foreign Office amid concerns about the widely-criticised police investigation into the murders of Miss Witheridge, 23, and Mr Miller, 24, whose bodies were found on Koh Tao on September 15.

Foreign Minister Hugo Swire told Thai charge d'affaires Nadhavathna Krishnamra there was 'a real concern' in the UK over the way in which the deaths have been treated and said it was crucial for the Thai authorities to investigate the killings in a 'fair and transparent' way.

And now it has emerged Britain's top envoy in Thailand has met police and Burmese officials amid concerns about the handling of the investigation which had also sparked concern from Amnesty International.

Mark Kent, the British ambassador to Thailand, said on Twitter he had taken part in a three-hour meeting with Thai police, the Burmese ambassador and a 'delegation' on the Koh Tao murders.

The two men charged with the killings, named in reports as 21-year-old bar workers Zaw Lin and Win Zaw Htun, were paraded in front of the cameras earlier this month having apparently made confessions which were reportedly later withdrawn amid allegations the pair were tortured.

Court proceedings have reportedly started against the two men, who have been charged with conspiracy to murder, conspiracy to rape and robbery, despite a plea to postpone the start of the pre-trial hearings which was rejected.

It is thought three potential witnesses from Burma will now testify at the court in Koh Samui. But the latest claims about the police investigation, which earlier this month saw the bizarre sight of the two men carrying out a reconstruction of the brutal killings, have raised further question marks about whether the victims' families are any closer to getting the justice they need.

Ahead of Miss Witheridge's funeral in Hemsby last week her devastated family issued a statement in which they said they 'hope that the right people are found and brought to justice'.

But even if it transpires these are the men responsible for the tourists' deaths, the devastated families of Miss Witheridge and Mr Miller will only be at the beginning of start of what could prove to be a long and arduous road to justice.

As demonstrated by the unusual news conference featuring the two suspects earlier this month, the criminal justice system in Thailand is different to what we have in the UK. Trials in Thailand can run for more than five years but even getting to court can prove a drawn out and protracted process.

Police last week submitted their investigation report on the murder of the two tourists to prosecutors at the prosecution office of Samui district.

But the 850-page investigation report is just the start of the process.

Anucha Charoenpo, deputy news editor of the Bangkok Post - one of the biggest English language newspapers in Thailand - said with police now having forwarded the case for consideration prosecutors will now have to 'set up a committee to vet the case whether there is evidence and witness to indict the two on theft, murder and rape charges or not'.

She said: 'If the two are indicted by the prosecutors, their case will have to be passed to the court for consideration. I do not know how long they will consider the case - maybe a year or two years.'

She described it as a 'shock case' and said people in Thailand were 'very sorry for what happened with the two British tourists' whose families grief can only have been exacerbated by recent claims about the investigation.

Thai police chiefs have called for the end of criticism of the investigation and said people should wait for the ruling of the Criminal Court on the case.

But with public doubt about the evidence gathered by officers growing almost the day the families of Miss Witheridge and Mr Miller who have already suffered beyond belief must at least brace themselves for the potential that there might be more crushing news to come.