Complex sentence: People interested in farming were said to flock to gatherings at Holkham-the so-called "Holkham shearings"-from all over Britain and from overseas; the'Shearings' were the fore-runners of today's agricultural shows.
Split into simpler sentences: People interested in farming were said to flock to gatherings at Holkham--the so-called "Holkham shearings"--from all over Britain and from overseas. The'Shearings' were the fore-runners of today's agricultural shows.