"But the genie is out of the bottle in relation to information on the internet."
His comments come as a report warns that more than 200 crimes a day are being committed against Britain's historic sites.
The official study found that more than 75,000 "heritage crimes" took place in 2011.
Criminals targeted World Heritage Sites, listed buildings, churches, parks and gardens, battlefields, conservation areas and shipwreck sites, according to English Heritage.
The damage suffered included metal theft, vandalism, graffiti and arson, with one in eight important sites being attacked.
Experts warn that the "alarming" figures show that Britain's history is being destroyed in an "insidious and often irreversible way" for future generations.
More than 30,000 listed buildings suffered substantial damage while anti-social behaviour around heritage sites was commonplace, the study found.
It added that the "most precious buildings were worst affected", with nearly a quarter of Grade I and II* listed structures subject to some type of criminal damage.
Mr Harlow added: "It's particularly depressing because the real difference between damage to an average building is you can go out and get material and labour and make an average building as good as new.
"We don't want them (historic buildings) to be as good as new, we want them to be what they were.
"They're valuable, not because of their monetary value and the cost of putting the repairs back is not the true cost of the damage done."
Uncovering a "worrying" rate of damage, the report also concluded that nearly one in five listed buildings were "physically harmed by crime" with more than a third of churches or religious buildings damaged.
But researchers, who uncovered an "unprecedented volume of information", believe the figure could be much higher as one in three heritage-related crimes go unreported.
Today's report surveyed the country's listed buildings of all grades, unlisted structures in conservation areas, scheduled monuments such as burial mounds and ruins and historic parks and gardens.
It stated: "There is a growing body of evidence that the risk of crime and anti-social behaviour facing designated heritage assets has grown considerably in recent years."
It concluded that metal theft was the "biggest single threat" to the country's landmarks, as gangs only saw "the metal and not the heritage". Official figures have shown more than 1,000 metal theft offences are occurring every week in Britain.
In recent months high-profile targets of criminals have included York Minster and the Bishop's Palace in Lincoln while the problem of metal theft was highlighted by the theft of a £500,000 Dame Barbara Hepworth bronze sculpture from Dulwich Park. Ancient covered walkways in Chester, known as the Rows, are being ruined by late-night revellers urinating on the 700 year-old woodwork,
The study found nearly a fifth of the country's 31,000 Grade I or II* buildings were subject to criminal acts while more than 63,000 Grade II buildings were targeted.
The report, compiled by the Council for British Archaeology and Newcastle and Loughborough universities, found that crimes such as metal theft was more likely to occur in the North while at least 750 sites were hit by "devastating" arson attacks.
It suggested that registered parks and gardens could be suffering the most amount of damage, although there were no "robust" figures to support it.
It also found more than 15 per cent of scheduled monuments - defined as unoccupied "nationally important historic structure significant for its archaeological value" - were damaged by unlicensed metal detecting and illegal vehicle access.
It also concluded that areas with fewer historic buildings and sites experienced "considerably more" instances of heritage crime.
Dr Simon Thurley, the chief executive of English Heritage, described the report's findings as "alarming", adding that historic sites were "suffering a substantial rate of attrition from crime".
"They are susceptible to irreversible harm," he said.
"Damage done to a listed building or an archaeological site can often not be put right and centuries of history will be lost forever. These places have an obviously high value to society.
"Their particular vulnerability warrants every effort to ensure they are still around for future generations to enjoy just as much as we enjoy them now."
The body has launched a new Heritage Crime Initiative with police and the Crown Prosecution Service after a sharp rise in crimes such as metal thefts.
More than 100 organisations have also signed up to a voluntary national body called the Alliance to Reduce Crime against Heritage, which aims to "galvanise" local support.
Richard Crompton, the chief constable of Lincolnshire Police and the ACPO national lead for heritage crimes, said virtually every force in the country was now running operations to target metal theft.
"There is a growing recognition across the police service of the impact of heritage-related crime," he added.
"While the theft of metal remains a significant challenge, these operations have resulted in many arrests and prosecutions across the country."
Janet Gough, the Church of England's director of cathedrals and church buildings division, said the report showed the "great burden from crime that is falling on places of worship" with many churches suffering from several times.
"This crime is hurting communities around the country as buildings central to the community and holding many generations of memory are desecrated.
"Churches are fighting back against crime with increased security measures and vigilance but are not able to bear the threat and cost of crime inde
finitely".
John Penrose, the Heritage Minister, admitted the report was "depressing reading".
He added: "When historic buildings and sites fall victim to vandalism, damage and theft, it's not just the owner who suffers.
"Very often the thing that's been stolen or damaged is literally irreplaceable, and the whole community is the loser."
The report said it did not address the "most fundamental question" of whether or not heritage crimes should be specifically recognised in law, while it could not say what drove such crimes.
Ministers have announced measures including banning cash transactions and introducing unlimited fines for people caught trading stolen scrap metal.
Two years ago, the National Trust teamed up with Google Street View to allow its landmarks to be accessed on the search engine's virtual mapping service.
