 Like all the Progressive MPs except Helen Suzman, De Beer lost his seat in the 1961 general election.He joined an advertising agency before moving on to work for the Anglo American PLC/De Beers diamond mining conglomerate.In the 1977 general election, he was returned to Parliament as an MP for what had become the Progressive Federal Party which had been formed that year through a merger of the Progressive Party and various other liberal groups of MPs.