Isobel Clara Reilly died after taking drugs at the North Kensington home of Brian Dodgeon, a 60-year-old researcher at the University of London, it is alleged.
The girl had been at a party hosted by Mr Dodgeon’s daughter, 14-year-old Beatrice Hadjipateras.
Sources said that at the party on Friday night — which was attended by about 10 teenagers — Isobel and Beatrice had found ecstasy and other drugs, believed to be ketamine and LSD, that are thought to have belonged to Mr Dodgeon and, along with two 14-year-old boys, had taken the drugs.
The group called 999 at about 4am on Saturday after Isobel, known as Issy by her friends, stopped breathing. She was pronounced dead later that morning.
Beatrice and the two 14-year-old boys were taken to hospital. Last night they were said to be in a stable condition but remained under observation.
Mr Dodgeon, who works at the University of London’s Institute of Education, was arrested by Scotland Yard on suspicion of drug possession and also on suspicion of child abandonment after allegedly leaving his daughter at home alone.
Since 1994 he has worked part-time while pursuing a parallel career as a teacher of the Alexander Technique from his home. The technique is an alternative therapy designed to help patients improve their posture.
Mr Dodgeon has also performed as a singer, specialising in 1930s-style cabaret, and as an experimental “postmodern” dancer.
Beatrice’s mother, Angela, was not arrested, and was at her daughter’s bedside. But police sources said they were investigating whether she should be arrested on suspicion of child abandonment.
Neighbours of the property — which is close to the home of Michael Gove, the Education Secretary — said the two adults had warned them on Friday afternoon that they were going out that evening and that there would be a party at their house that was likely to be noisy.
Last night Isobel’s parents, Patrick Reilly and Lynne Jones, both 55, released a tribute to their daughter, saying that they hoped her death would serve as a warning to other youngsters experimenting with drugs.
They said: “Isobel’s family and friends are devastated and heartbroken by her untimely death. We hope that if anything positive comes from this dreadful event, it is that others will make the right decisions to be safe and well in the future.
“We would very much appreciate time to grieve for our beloved Issy in private. If anyone has any information concerning Issy’s death could they please contact the police.”
Friends of Isobel, who attended the Chiswick Community School, posted tributes on Facebook. A memorial is planned today with more than 200 teenagers expected to attend.
One girl wrote: “I wish you could walk into school on Tuesday with your bright blue shiny eyes, your long red hair and your gorgeous smile. But that isn’t going to happen. I can’t wait to see you when it’s my turn.” Tony Ryan, the head teacher of the school said: “Isobel was an extremely popular girl at our school and counted many of her fellow pupils as friends. Her tragically early death is devastating news to everyone associated with the school and all our thoughts are with her family at this time.
“As pupils and staff return to school this week following the Easter holidays, we must now focus on assisting all those affected to come to terms with this terrible course of events.” The debate over the safety of ecstasy was brought into sharp focus in 1995 when 18-year-old Leah Betts died after taking an ecstasy pill. An inquest showed she had been killed by drinking a large amount of water while under the influence of the drug.
In 2009 the UK Advisory Council on the Misuse of Drugs, the body that advises the Government, recommended that ecstasy be downgraded to a class B drug. But the recommendation was rejected by the Home Office.
Prof David Nutt, who headed the council at the time, said the drug was no more dangerous than horse riding.
Mr Dodgeon has lived at the £1 million Victorian terrace house since 2004 and has a 27-year-old son called George.
Mr Dodgeon studied at Bristol University, where he gained a first-class honours degree in pure maths and postgraduate diplomas in social administration and applied social studies.
In the 1970s he ran a shelter for homeless men, and later worked as an inner-city social worker, welfare rights adviser and campaigner. Mr Dodgeon also worked as a social worker for Hammersmith and Fulham council.
At the Institute of Education, Mr Dodgeon works on a project called the National Child Development Study. He joined the institute in 1990 as a research fellow specialising in the computing aspect of the Office for National Statistics’ Longitudinal Study. He speaks French and Spanish.
A spokesman for the Metropolitan Police said last night: “Police have launched an investigation following the unexplained death of a 15-year-old girl in west London.
“A 60-year-old man was arrested by police investigating the incident on suspicion of possession of drugs and child abandonment. He was subsequently bailed to return on a date in June.”