Complex sentence: The First World War halted production, which did not resume until 1922 in Coventry Montgomery continued to experiment with sidecar design and actually competed himself in the 1923 Isle of Man TT sidecar race.
Split into simpler sentences: The First World War halted production, which did not resume until 1922 in Coventry. William Montgomery continued to experiment with sidecar design and actually competed himself in the 1923 Isle of Man TT sidecar race.