Может, правильнее "Суд магистрата на улице Грейт Мальборо"?
Nos. 19–21 : Great Marlborough Street Police Station And Marlborough Street Magistrates' Court
Дом 21:
"...In 1792 an Act of Parliament 'for the more effectual administration of the office of a justice of the peace in such parts of the counties of Middlesex and Surrey as lie in and near the metropolis' provided for the establishment of seven public offices. Three justices were to be attached to each office, and they were empowered to employ sufficient constables 'for the more effectual prevention of felonies'"