Why did the Conservatives hold Power either unilaterally or in National Government between 1868 and 1992?

Between 1968 and 1992 the Conservative Party was the dominant British Political party holding power longer than both the Liberal and Labour Partys put together. The Conservative Party is traditionally representative of the middle and upper classes but during the period, which included an increase in the franchise on a few occasions, the Conservatives were able to adapt their flexible ideology and political message to attract new Tory voters. From this ideological flexibility the Conservatives benefited significantly attracting voters who would not be natural Conservative voters for example the transition to One Nation Conservatism secured many urban industrialised seats….(short extract)