They called it the Darcy effect - in the year that the BBC screened its now legendary adaptation of Pride and Prejudice visits to historic properties soared.
Lyme Park in Cheshire, cast as Darcy's country house, Pemberley, saw a 178 per cent rise in visits on the preceding year. In the same year - 1996 - the revenue earned from visits to stately homes grew by 6 per cent to pound;212 million, according to the English Tourist Board which collates data covering visits to all historic properties including churches, cathedrals, ancient monuments and conservation areas.
In spite of the attraction of stately homes and castles, historic properties have to work hard to attract visitors in a market of increasing consumer sophistication and choice, especially if the property is charging for admission. Given the constraints of working within a listed and often delicate building, it is nearly impossible for them to compete with the technological wizardry which enables museums and larger attractions to pep up tired exhibits or to re-invent themselves entirely.
A historic property benefits to a large extent on the fame of its previous incumbents. It is not just Mr Darcy who has pulling power. Blenheim has the first Duke of Marlborough, the Royal Pavilion in Brighton has George VI. Hampton Court has Wolsey and Henry VIII, and Osborne House has Victoria and Albert.
But not all historic properties can boast a celebrity link, or are blessed with the resources of the owners of Windsor Castle, for example, which last year opened a four-classroom education centre; or Hampton Court, which has around 149 paid staff and that's out of season.
For these others, ingenuity and creativity are the reason schools continue to visit.
There is considerable variation in the range of facilities available at historic sites. Many properties will offer teachers a free familiarisation tour, from which they are expected to structure a later visit to suit the needs of their particular group. Nearly one third of properties offer guided tours; the National Trust has guides in each room to answer questions. Other properties go one step further with "interpreters" in period costume who help bring properties to life. Actors can similarly be used to dramatise a particular event or period relevant to the property or the studies of the visiting group.
Many sites include audio-visual presentations or slide shows, or pre-recorded tapes. English Heritage, which manages about 400 sites all of which are free to groups, has installed several CD-Roms on the purpose and function of castles.
The Heritage Education Trust administers the annual Sandford Awards for excellence in educational services and facilities in historic properties. Since 1978, these have recognised the great learning potential of dressing up in costumes, handling artefacts, role-playing, making music and drama in historic settings and discovery trails.
There were slightly fewer properties open to the public last year (2,013) than in 1996 (2,017) which suggests that for some owners at least, the exercise is simply not worth it. A recent study of Knebworth House near Stevenage found that the number of visitors there would have to increase 15 times to supply the revenue needed to keep the house and grounds in good condition.
Although the school market is a lucrative one, there is no guarantee that a stately home or castle can make money on the strength of good looks alone.