Penny Olsen, who owns the Research Workshop, spends her time answering these questions. To her business clients, Olsen is a historical architectural researcher; others call her the house detective.
Olsen became interested in the history of buildings after her children had grown up. She embarked on an Open University course in architecture. The Conran group saw Olsen's thesis on the Michelin Building and used her work as part of their planning application for the Bibendum restaurant. Olsen was encouraged by this. "I thought, well, if the Conrans think my work is useful, maybe other people will, too."
She sent out dozens of letters to property developers and got two jobs immediately, to research one site in the City of London, another in Reading, for brochures of the area.
When the property development market went into a slump during the recession, Olsen changed tack and targeted her work more at private individuals who wanted to know more about their family home. She now numbers famous film and television personalities among her clients as well as members of the aristocracy. "I love what I do. My work is like a jigsaw, piecing together information, bit by bit, until I have the whole picture."
Olsen builds up her historical jigsaw using maps of the area from a variety of different periods, planning applications, land tax assessments and even drainage records. Structural and interior design details help her plot the course of the property's development while rate books, cross- referenced with census returns, electoral registers and marriage records give clues of previous residents.
"Sometimes clients just want a list of names of people who have lived in the house through the years or a simple report of its historical backgrounds. Other people want a full-blown story, beautifully presented. I often work to a budget and a lot of my work for private customers is in producing surprise gifts for family members."
Each project takes up to six months; prices range between pounds 250 and pounds 3,000 and are presented as either a slim sheaf of papers between simple card or full leather-bound book, complete with pictures of previous residents, maps of the area and original elevation plans of the property at various stages.
"Sometimes the information is quite easy to find. But I had one building that was in a remote area and I wasn't sure I would be able to establish much. However, with a few days of research I found out that the building had been owned by Balliol College, so a wonderful archive existed."
One set of clients was delighted to find out that their house was once used as a flagellation brothel. Other stories are not so uplifting. She decided not tell one set of owners that their home was built on a plague pit.
Visitors' books can also be a rich source of history. Olsen unearthed one that the Kray Twins signed on their regular tea-time visits to the property. Olsen's own visitors' book is signed by Elizabeth Taylor and Liberace. Both were customers at the chemist shop she and her husband owned on the King's Road during the Sixties.
Local archives and local people play a great part in her work. Older people's memories of events, scandals and personalities provide a sense of how the area grew in a way that statistics cannot.
Ironically, she has never had time to research the houses she has lived in. "The owners of our old house have asked me to look into the history of the property for them. I can't wait to see what I find."
The Research Workshop 0171-935 2360