Let's get our dates straight

Diana Spencer is back. Or so controversial marketing for The Duchess suggests. Inspired by Amanda Foreman's biography and starring Keira Knightley and Ralph Fiennes, the film - released last week - explores the life of Georgiana, Duchess of Devonshire, doyenne of 18th-century high society and a powerful political hostess.

However, it is the Duchess' dynastic link to the 20th century's most celebrated Princess of Wales and an implied common experience between the two women, rather than the 18th-century setting, that dominates the promotional material.

The film's director, Saul Dibb, along with Foreman and Knightley, have all criticised the strategy. And what I saw unfolding on set while I was working as historical adviser on the film was not so much a thinly veiled take on the 20th century as the director's probing of the 18th-century power elite.

A very Georgian story of culture and authority underpins the film. The fact that the modern drama of the Diana story has overshadowed this historical context should be a call to arms for historians.

It is unclear when Diana was drafted in help market the film, but perhaps the way in which 18th-century history is most often encountered - or not encountered - has played a part. This can hardly be blamed on the film's makers and marketers.

Academics have long decried the "Hitlerisation" of history, which leaves children wise to dictators' misdeeds but not much else. While there have been attempts to rectify this, first-year university students still arrive with little knowledge of Britain in the 1700s.

The "Glorious Revolution" is a revelation, the Jacobites a mystery, the Whigs unheard of, and few can name an eminent Georgian. Outside the classroom, public appetite for 18th-century British history appears - superficially, at least - to be strong. National Trust properties are popular, but these offer only partial windows into the past, shaped more by our own preoccupations than by 18th-century experience.

Biographies of gorgeous Georgians sell well. However, as biographer Kathryn Hughes has complained, some recent works are succumbing to a modern obsession with celebrity scandal and risk shoehorning 18th-century women into Paris Hilton's Manolo shoes.

From this perspective, it is less surprising that The Duchess trailer eschewed an apparently unfamiliar history in favour of showcasing familiar celebrities and heritage interiors. Arguably, the trailer conforms to mainstream portrayals of the period. And it is this bigger picture that should concern us.

Academics, often bruised by cold-calling television researchers looking for fast and dirty answers, can be reluctant to fraternise with the media. Equally, pompous, bookish preaching has left "historical advice" dubbed "hysterical advice" by frustrated film-makers. There must be scope for more co-operation.

The research councils increasingly demand knowledge transfer as a condition of grants. Trailer tutorials for A-list actors may not constitute the knowledge economy that was envisaged, but encouraging academics to work outside their comfort zone certainly is.

I found the work of historical adviser invigorating. Admittedly, long stints on set sometimes felt like a nightmare viva. Queries came at any time and on any topic, from 18th-century politics to historically correct swear words. Nonetheless, easy access to the props did help me to generate ideas for a forthcoming research project on material culture.

The threatening presence of a crowd of wigged women in hooped gowns, each towering over six feet tall, brought home why 18th-century men so feared the "power of the petticoat". I also defy any colleague not to be cheered when your one-minute "lecture" on political corruption is rewarded with boisterous applause and wolf whistles.

Refusing to participate in how history is told in the public domain is surely counterproductive. Instead of playing down and avoiding popular histories, we might serve the subject better by engaging more thoroughly. The conflation of The Duchess with Diana stands as a timely reminder. It is time to demonstrate that history matters in its own right, on its own terms.