The ITV series Doc Martin is worth millions to the Cornish economy, according to Visit Cornwall.
The cast and crew are currently in Port Isaac filming series 8 of the hit drama series.
The programme, about a grumpy doctor with a fear of blood is now broadcast worldwide.
''We've actually done research into the impact of Doc Martin and of the viewers who watch Doc Martin 27 percent said it was their trigger for coming to Cornwall, and that's not just in the UK. We get an awful lot of Australians, Americans and Canadians who come to Cornwall and want to go to Doc Martin country, and want to go to Port Isaac.''
The Doc Martin effect has seen a growth in demand for holiday cottages by international tourists.
"The Doc Martin crew book with us so they're down for 18 weeks at the moment taking 20 of our 80 cottages. Over the years Doc Martin has drawn a very good international audience, so we do get a much better international clientele coming down to see where they film, so it has had an impact definitely.''
Up to twenty Doc Martin fans who call themselves 'Clunatics' regularly visit from America to watch the series being filmed.
"The programme has everything it's a love story, it's funny, it just has everything, it's drama and Martin is just fabulous. There's no better actor that can do what he does for this character, and he's brilliant.''
You can watch Kathy Wardle's full report below: