The devastated mother of a university graduate who was strangled to death before the killer set fire to her flat has spoken of her shock after discovering her daughter worked as a prostitute.

Speaking for the first time about Andrea Waddell's murder, distraught Sonia said she could not understand who would want to hurt her "harmless and beautiful" daughter.

Police initially believed Ms Waddell - who was born Alexander John but had a sex change operation - had died in an accidental blaze.

But the results of a post-mortem examination revealed she had been murdered.

The 29-year-old was found on Thursday after a neighbour alerted emergency services to the fire in her flat in Upper Lewes Road, Brighton.

She moved to the city about five years ago to study for a Master's degree in Social and Political Thought at the University of Sussex, graduating in 2006.

Her mother Sonia, of Reading, said she was stunned to discover from Sussex Police that her daughter was a sex worker.

She said: "Andrea was a wonderful daughter and we are amazingly proud of her, in spite of her having a life which we didn't know about.

"We had no idea she was working as a prostitute and we were shocked to find out.

"But she has never hurt anybody and has never done anything to upset anyone.

"She was there for everybody, a generous and caring person.

"She was a beautiful daughter and had been through so much."

Ms Waddell, who was born Alex, attended Durham University from 1999 to 2001, graduating with a degree in philosophy.

In a statement released by Sussex Police, Ms Waddell's family said their child was born Alexander John but saw a psychiatrist about his ambivalent gender feelings as a teenager growing up in Reading, Berkshire.

At the age of 14 he was diagnosed with scoliosis (severe spinal curvature), and after surgery developed fibromyalgia, a permanent condition of chronic pain.

He began hormone treatment while studying philosophy at Durham University and ended his three-year course as Andrea Joanna.

He then underwent gender surgery while studying for a master's degree in social and political thought at the University of Sussex.

A man 42-year-old Brighton man is today still being questioned by detectives in connection with Ms Waddell's death.

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