In 1972, Hunter S. Thompson set about covering the presidential campaign, paying special attention to the Democratic Party’s George McGoven as he failed to get into office.

Fear and Loathing on the Campaign Trail '72 was serially published by Rolling Stone throughout the year. In one of the articles Thompson makes a poignant comparison to a campaign that happened in Texas in which Lyndon Johnson attempted to create a rumour to denounce his competitor.

It reads: “This is one of the oldest and most effective tricks in politics. Every hack in the business has used it in times of trouble, and it has even been elevated to the level of political mythology in a story about one of Lyndon Johnson’s early campaigns in Texas.

“The race was close and Johnson was getting worried. Finally he told his campaign manager to start a massive rumour campaign about his opponent’s life-long habit of enjoying carnal knowledge of his barnyard sows.

“Christ, we can’t get away with calling him a pig-f****r,” the campaign manager protested. “Nobody’s going to believe a thing like that.”

“I know,” Johnson replied. “But let’s make the sonofab****h deny it.”

David Cameron holds Florence the piglet, one of the two which he donated to Coggs Farm in 2014 (David Hartley/REX Shutterstock)