Complex sentence: As portreeve, Gervase would be likely to live near the scene of his duties; his house would have opened directly onto the harbour, at a time when there was no wall running along Winkle Street from the Water Gate to God's House Gateway.
Split into simpler sentences: As portreeve, Gervase would be likely to live near the scene of his duties; his house would have opened directly onto the harbour. There was then no wall running along Winkle Street from the Water Gate to God's House Gateway.