British police who travelled to Thailand to review the probe into the murders of Hannah Witheridge and David Miller are due to return to the UK, having completed their work "as far as possible".
Officers from the Metropolitan Police flew out last month to work with the Royal Thai Police after an agreement between David Cameron and military ruler General Prayuth Chan-ocha.
It followed international concern about the way the case has been handled by the Thai authorities.
Mr Miller, 24, from Jersey, and 23-year-old Ms Witheridge, from Great Yarmouth in Norfolk, were found dead on a beach on the holiday island of Koh Tao in September.
Two Burmese men, named as 21-year-old bar workers Zaw Lin and Win Zaw Htun, were charged with the killings and paraded in front of cameras after apparently making confessions, but these were later reportedly withdrawn.
UK police concerns are understood to have been around the verification of DNA samples of the suspects and allegations of their mistreatment.
Scotland Yard said officers will compile a report from their review.
" Detectives from the United Kingdom who are currently in Thailand reviewing the investigation into the murders of Hannah Witheridge and David Miller have completed their work, as far as possible," the Met said in a statement.
"They will now be returning to the UK to compile their report and to update the families of Hannah and David on their findings.
"The police team wish to thank the Thai authorities for facilitating the visit."