Forget your preconceptions about the civilised, sparkling, white cityscapes of the ancient world: Real-life Pompeii was an altogether more sordid proposition, as Cambridge classicist Mary Beard is set to explain.

In an hour-long documentary on BBC Two tonight, Professor Beard will draw on some of the latest finds, as well as her own experience researching Pompeii and Ancient Rome, to uncover little-known facts and bust some long-standing myths about the most famous excavation site in the western world.

The programme, Pompeii: Life and Death in a Roman Town, starts with a simple premise - that an ancient town known best for the disaster in which it was destroyed, actually tells us most about how the average Roman lived.

Rather than focus on the eruption of Mount Vesuvius in AD79, therefore, Professor Beard instead examines the details of daily life revealed by the buildings, skeletons and other remains which were preserved when Pompeii was buried under several feet of volcanic ash.

In particular, the documentary draws on new evidence from a single find: 54 skeletons which were found in a cellar in Oplontis, three miles from Pompeii's centre.

Using the latest forensic techniques, researchers have been able to answer key questions about the lives of these people - including how well-nourished they were and what diseases they had survived.

Sex itself is one of the recurring themes in Professor Beard's investigation into the lives of around 12,000 people who inhabited what she describes as a bustling resort town that resembled "a cross between Las Vegas and Brighton".

The remnants of Roman graffiti found on the site, which are replete with lewd talk and sexual gossip, combine with erotic posters and dubious frescoes to reveal just what a sexualised bunch the Pompeiians of the first century AD were.

Contrary to the gleaming, elegant Hollywood image of the Roman world, the town was also far from clean. Rather, Beard shows it to have been a foul-smelling, noisy place, where stepping stones had to be placed on the streets so that pedestrians could negotiate the fetid water that periodically flowed down them.

Even the baths - supposedly civilised centres of cleansing, lacked some basic features modern bathers would consider essential. Beard points out the shortage of plugholes in particular - meaning that bathers most likely often immersed themselves in a mixture of water, sweat, urine and bacteria.

Yet more evidence comes from a surviving cesspit at Herculaneum, close to Pompeii. Guided by Andrew Wallace Hadrill, the Master of Sidney Sussex College, who has excavated the site, Beard inspects the surviving contents of ancient Roman lavatories and finds out what ordinary Pompeiians had for breakfast.

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More information: Professor Beard is Professor of Classics at the University of Cambridge and a Fellow of Newnham College. Tonight's documentary is based on her book, Pompeii: The life of a Roman town, which is published by Profile. The programme itself will be shown on BBC Two tonight at 9pm.