Complex sentence: During Victorian times the town was a backwater, escaping large-scale development, and the town centre remains very much as it must have been in the mid-seventeenth century, when the houses were rebuilt after a great fire.
Split into simpler sentences: During Victorian times, the town was a backwater, escaping large-scale development. The town centre remains very much as it must have been in the mid- 17th century, when the houses were rebuilt after a great fire.