The girlfriend of a teenager killed in a Thailand coach crash has spoken of her heartbreak for the first time, as his mother demands the truth about her son’s death.

Elsie Lauchlan, 19, lost her boyfriend of four years, 19-year-old Max Boomgaarden-Cook, in the June crash.

And she described the Brixton teen, who was killed along with school friends Bruno Melling-Firth, 19, and Conrad Quashie, 19, as her "best friend".

The group, from the Charter School, Dulwich, were travelling to the northern capital of Chiang Mai on the fourth day of a nine-week gap year trip, when their overnight coach was hit by another bus in Khlong Khlung, in the Kamphaeng Phet Province.

Mr Boomgaarden-Cook, who was due to enrol with his girlfriend at university in September, died instantly.

Miss Lauchlan, now a sociology student at Manchester University, spoke exclusively to the Streatham Guardian about her grief.

She said: "It has been incredibly hard. I was absolutely distraught [when he died]. I have lost someone I was madly in love with. I have lost my best friend and the last five years of my life. It is really hard to get my head around.

"He was hugely passionate about history and travelling, which is why it was so heartbreaking. He only had four days out there. It should have been the best summer of all our lives."

The mothers of all three teenagers are campaigning for the Thai authorities to release more information about the incident and have written a letter to Foreign Secretary William Hague for help.

Max’s mother, Polly Cook, of Baytree Road, Brixton, who has seen her case championed by Streatham MP Chuka Umunna, said they have one year to mount a legal case, but have been told by Thai officials that a police investigation could take a year itself.

She said: "We have been told absolutely nothing. We have been treated as though we were Thai, and I have found out that that is not very nice."

Following the accident, the Foreign Office changed its advice to Britons travelling in Thailand, stressing the increased risks of road travel in the country. it added 347 Britons died in Thailand last year.

According to police statistics, almost 13,000 people were killed on Thai roads in 2005 – more than five times the amount killed in UK road accidents, where there is roughly the same population.

Commenting on her son’s death, she said: "It is extremely painful. It is really difficult.

"You wake up in the morning and you are hit by the reality. I have a lot of concerns for his brothers.

"I thought it was a rite of passage – it was part of him growing up.

"It was not just a party, it was an experience."

Her solicitor Clive Garner said: "I hope that the investigations proceed quickly so that Polly, and the families of the other two young men killed, can get the answers and the justice they deserve."

Miss Lauchlan said: "Max never got the chance to go to university to show everyone how talented and what a beautiful person he was."