Complex sentence: Mrs. Wilberforce's house, No.57, was a set built at the western end of Frederica Street, directly above the southern portal of Copenhagen Tunnel on the railway line leading out of King's Cross railway station.
Split into simpler sentences: Mrs. Wilberforce's house, No.57, was a set built at the western end of Frederick Street. It was directly above the southern portal of Copenhagen Tunnel on the railway line leading out of King's Cross railway station.