Complex sentence: A right to hold a weekly market was first granted in 1715, although there have been several periods since then during which the market did not function, for example from the late 1700s until c.1850.
Split into simpler sentences: A right to hold a weekly market was first granted in 1715. However, there have been major gaps when the market didn't function, for example from the late 1700s till c.1850.