Complex sentence: Four ornate iron gas lamps were included in the bridge's design, forged by Henry Longden of Sheffield, although thieves removed their lead supply pipes, and so the bridge was unlit on the day it opened.
Split into simpler sentences: Four ornate iron gas lamps were included in the bridge's design, forged by Henry Longden of Sheffield. However, thieves removed the lead gas pipes which supplied the lamps, and so the bridge was unlit on the day it opened.