Complex sentence: The Hill has had a great deal of work carried out by volunteers (SHV, led by John Smallwood), since 1992, in an attempt to restore the open views over the Severn Vale.
Split into simpler sentences: The Hill has had a great deal of work carried out by volunteers (SHV, led by John Smallwood), since 1992. They have attempted to restore the open views over the Severn Vale.