Complex sentence: The storehouse was built by the Board of Ordnance as a "sea storehouse" (a repository for naval ordnance supplies); further storehouses were added to form the north and east sides of the square in 1808-10.
Split into simpler sentences: The storehouse was built by the Board of Ordnance as a "sea storehouse" (a repository for naval ordnance supplies). Further storehouses were added to form the north and east sides of the square in 1808-10.