Complex sentence: From the early to mid- 1970s, the lack of compulsion slowed the process of metrication down, a draft order was prepared to completed the process, but the Government, which had a very small majority, declined to proceed with the order.
Split into simpler sentences: From the early to mid- 1970s, the lack of compulsion slowed the process of metrication, so a draft order was prepared to complete the process. However, the Government, which had a very small majority, declined to proceed with the order.