Complex sentence: He introduced this idea to Paul Chambers, then on the board of the Inland Revenue, and the idea, which became the PAYE system, would be tested in 1940--1941 and introduced permanently in 1944.
Split into simpler sentences: He introduced this idea to Paul Chambers, then on the board of the Inland Revenue. The idea, which became the PAYE system, would be tested in 1940--1941 and introduced permanently in 1944.