Heath's election triumph - the only one in the four campaigns he fought as Tory leader - gave his party a solid working majority for the parliament ahead.

He had taken 330 Commons seats on 46.4% of the vote, with Labour lagging behind on 288 seats and 43% of the vote.

After seeing their number of MPs rise into double figures in the previous parliament the Liberals fell back to six MPs, taking just 7.5% of the vote.

The Scottish National Party also picked up its first seat at a general election, taking the Western Isles from Labour.

The swing to Heath of 4.7% nationally was so large in some seats that the BBC had to extend its election 'swingometer' to illustrate the shock results.

But if the swing was high, the turnout definitely was not. Despite, or perhaps because, 18-year-olds were able to vote for the first time turnout was down to 72%, the lowest since 1935.

The surprise result may have been a combination of the opinion polls overestimating Labour support and disillusionment or plain disinterest keeping the parties’ supporters at home.

But at this stage of the post-war period Labour and the Conservatives were almost evenly matched in their possession of power. Up to 1970 Labour had spent 12 years in Downing Street and the Conservatives 13.