TV show Outlander is becoming “a victim of its own success” as herds of tourists flock to sites made famous in the series, a Scottish heritage body has warned.

Many of the sites where the fantasy series, inspired by novels by Diana Gabaldon, was filmed were previously off the beaten track. But the popularity of the Jacobite drama is putting pressure on attractions such as Doune Castle in Stirling, Linlithgow Palace and Blackness Castle in West Lothian, and Craigmillar Castle in Edinburgh which Historic Environment Scotland (HES) has allowed producers to use.

Thousands of tourists are now “trampling” on the sites, forcing rangers to patrol previously uninhabited areas.

Audrey Jones, head of filming at HES, said: “We’re having issues with sites that are just so popular now.

“We’re looking at timed tickets, capacity management and

investing in infrastructure to make it more pleasurable for people. If you had come to Doune Castle five years ago there would probably have been hardly anyone else there. You don’t want to be rammed in with a thousand other people.

“It’s not a nice experience.

“There are obviously people who have never heard of Outlander and don’t understand why this beautiful castle that they came to five years ago is suddenly mobbed.

“It’s about making sure that they also have a good experience.

“Conservation is our raison d’être.

“We’re trying to

make sure that people don’t trample over sites like Clava Cairns, the Ring of Brodgar and the Callanish Stones.”

Since filming began in 2013, there has been a 67% increase in visitor numbers at sites featured in the series.

Jones added: “People flying [drones] across properties where Outlander has been

filmed to get aerial shots has become a major issue for us.”