The mother of a backpacker murdered in an unsolved killing in Thailand 10 years ago has spoken of her long wait for justice for her daughter.
Kirsty Jones, 23, from Tredomen, near Brecon, Powys was raped and strangled at a guesthouse on 10 August, 2000.
Sue Jones says she will never give up the fight to see the murderer caught.
Dyfed-Powys Police recently questioned four Britons and a UK-based Thai national as a routine part of the inquiry, but they are not suspects.
Despite a number of arrests, no charges have ever been brought.
But Dyfed-Powys Police said there were lines of inquiry which still "needed to be resolved, and a number of people still of interest to detectives".
In recent weeks, five people who were in Chiang Mai, the city where she died, were interviewed by the Dyfed-Powys force. But they were not arrested and are not considered suspects.
This was a result of Dyfed-Powys Police having called on the Thai authorities to supply them with a letter of request, an official document, which enables British police to interview people on behalf of an overseas force.
Without the letter of request, the evidence would not be valid if the case came to court in Thailand.
The interviews will be passed to the Department of Special Investigations in Thailand, which has been reviewing the case since 2006.
Mrs Jones said securing the document was a "major breakthrough", but the interviews had not helped identify the killer.
Her daughter, a Liverpool University graduate, was found dead in a room at the Aree guest house in Chiang Mai, which is north of the country's capital, Bangkok.
She was three months into a two-year around-the-world trip when she was murdered on 10 August, 2000.
Dyfed-Powys Police later secured the killer's DNA, belonging to a man of south-east Asian origin, following a visit by two senior officers to the crime scene.
Mrs Jones said she was optimistic her daughter's murderer would be found.
She told BBC News: "I am always optimistic.
"It's a waiting game. It's been a long time, but we have the DNA and that's where the answer lies.
"I've never actually thought they wouldn't catch anyone, but I do get weary sometimes because it's such a long and slow process, but you can't give up. I'll never give up."
Ch Supt Steve Hughson has been involved in the case from the start, and along with his colleague Det Ch Supt Steve Wilkins, they have visited Thailand twice to help with the investigation.
The force's involvement in the inquiry started in September 2001 after the family became frustrated by the way the Thai police were handling the hunt for the killer.
"The 10th anniversary is a significant milestone," said Ch Supt Hughson.
"The focus is still actively on this case and that is testament to the concern we have shown to it, and the support we've given to the family.
"We recently received a letter of request from the Thai authorities to interview a number of UK-based witnesses, four British nationals and a Thai national, which is now complete.
"There were some points that needed clarification.
"We're in the process of analysing this and then we'll send it to the Royal Thai Police."
Ch Supt Hughson said there were lines of inquiry which still "needed to be resolved, and a number of people still of interest to detectives".
He added that police had the killer's DNA and all they needed was a name.
He said: "I am confident that one day somebody will be caught for this. We're doing everything we can to make sure it (the case) comes to a successful conclusion, and we're making sure it's on the political agenda."
In 2007, Brecon and Radnorshire MP Roger Williams asked Tony Blair to meet the Jones family during prime minister's questions in the House of Commons, and Ch Supt Hughson said a brief about the case was given to every Foreign Office official who visited Thailand.
On Wednesday, the BBC News website will carry a longer interview with Sue Jones, Kirsty Jones's mother.