In recent years Ms Verstappen has given lectures at universities on male sexual desires.
Sonia Verstappen stated to work as a prostitute of her own volition at the age of 22.
She says that she did so as she was jealous of the women that were able to go upstairs with clients while she sat at the till of the brothel where she worked.
She has never had a pimp and was able to choose her clients. Ms Verstappen’s door was always kept firmly shut for bedraggled, unkempt, dirty or drunken men.
Over the years Sonia Verstappen has campaigned for prostitution to be given legal recognition as a profession as this would offer greater protection to the thousands of women in Belgium that work as prostitutes.
She has also slammed the lack of action by the authorities against the problems of forced prostitution and people trafficking that are all too prevalent in the red light district around Brussels North Railway station.
Sonia Verstappen was noticed by lecturers at Brussels Francophone Free University and gave an annual seminar at the university entitled ‘Desire, fantasy and screwing’ in which she examined sexual desires in men.
She currently gives talks at psychology departments at various Francophone universities and colleges of higher education.
The 59-year-old has decided to call it a day in order to concentrate on the Masters course in anthropology that she is currently taking at Louvain-la-Neuve University.