A York firm is set to resolve one of the major riddles of Stonehenge.

A team from QA Research will be among the 20,000 visitors heading for the sacred heritage site in Wiltshire tomorrow to mark the summer solstice.

QA Research, which is based in St George's Place, has been commissioned by English Heritage, the site owner, to conduct a fact-finding survey into visitor profiles and habits.

The object is to "provide a memorable experience for attendees that travel from all round the world and also help safeguard Stonehenge's future".

In other words, the York company's task will be to discover for the first time exactly who turns up and how they can best be served.

It is a far cry from the 1980s, when the sacred site was closed to the general public and a four-mile exclusion order put in place around it following a series of problems.

Stonehenge was reopened for the summer solstice in 1999 and there have since been relatively few hitches.

Up to 300 visitors to the site will be surveyed by the QA researchers to discover who they are and thier personal motives for going there.

Stonehenge director Peter Carson said: "Through the results of the survey, English Heritage will be in a better position to build a sustainable future for the annual gathering, which ensures that public safety and the conservation of the monument always remain a priority.

"With access to celebrate the solstice at Stonehenge growing over the past six years since its reconception, it has been increasingly necessary to formalise the gathering information that relates to visitor profiles, habits and behaviour rather than relying on anecdotal observations."

Nicky Green, research manager of QA Research's heritage and attractions department, said: "A lot of different interest groups and community groups visit Stonehenge.

"Some go with religious interests at heart, such as druids, while others go out of curiosity or have some kind of attachment to the site. English Heritage needs to know it is catering properly for all these people."

Updated: 10:59 Monday, June 20, 2005