THE aggressively loud volume of the average posh person is in fact a product of evolution, scientists believe.

Their tendency to talk incredibly loudly or simply shout most of the time was previously dismissed as rudeness, but evidence suggests that poshos bellowing at both oiks and their red-trousered chums has a genetic basis.

Professor Henry Brubaker of the Institute for Studies said: “We’ve all seen this puzzling behaviour. Counterintuitively, it often occurs when excessive sound levels are not needed at all, such as in the quiet carriage of a train, or conversing with someone a mere foot away.

“Our research has narrowed down the causes. Firstly, there is the the sheer size of posh people’s houses. The rich needed to vocally project or they risked their servants being unable to find them in their many bedrooms, dining rooms and studies, leading to starvation.

“There was was also the occasional need to communicate with the working classes, which meant shouting over deafening factory machinery to tell employees to stop making such a bally fuss over a severed hand.

“Obviously society is more egalitarian now, but even today a fox hunter may need to give a proletarian a bollocking for their cat being ripped to pieces by dogs due it irresponsibly existing.

“We also must not forget that microphones are a relatively recent invention and in Victorian times the rich needed their voices to carry when performing insipid operettas and sketches in their drawing rooms, their primary means of finding a mate.

“So we can see that shouting like a wanker is vital to the continuation of the subspecies. Without it they would simply be unable to inbreed.”