Complex sentence: The firm reached its apogee in the early Victorian period, when it employed over 2000 and its reputation for engineering and bridge building was worldwide, and to which the striking High Level Bridge across the Tyne stands as monument.
Split into simpler sentences: The firm reached its apogee in the early Victorian period, when it employed over 2000 and its reputation for engineering and bridge building was worldwide. It built the striking High Level Bridge across the Tyne stands as monument.