Free online advertising London

Free marketing: 1999 rom-com Notting Hill generated the equivalent of £19.5million in ad spend for London

Likewise, fans tweeting about Harry Potter and its filming locations resulted in a tourism boost for the UK

Richard Curtis' 1999 rom-com Notting Hill, starring Hugh Grant and Julia Roberts, generated the equivalent of £19.5million in online ad spend for London, while Harry Potter generated £10.4million.

Mentions of Game of Thrones led to the equivalent of £1million in advertising for Malta, where the HBO series filmed the Dothraki scenes for season one.

Hit series Sherlock, starring Benedict Cumberbatch, garnered £10.8million worth of advertising spend on social media, while Wallander yielded £17.9m for Ystad in Sweden.

Landmarks: Sherlock, starring Benedict Cumberbatch, garnered £10.8m worth of ad spend

Spectacular scenes: Malta got a tourism boost worth £1m in advertising thanks to Game of Thrones

Almost 35 million comments and interactions on social media relating to four European locations (London, Malta, Ystad in Sweden and Apulia in Italy) were analysed.

The new insight into the links between film and television productions and tourism was revealed at an international screen tourism conference today by Film London, the lead partner for major European project EuroScreen.

Adrian Wootton, CEO of Film London and British Film Commission, said: 'This research shows that productions don't just sell cinema tickets and box sets, they also sell the places where they're made. Quite simply, this is free advertising, and emphasises the power of screen productions as a tourism driver.'

'#Malta on the bucket list after watching #GOT!': Tweets translate to tourism dollars for locations on screen

SCREEN TOURISM 'EARNINGS'

LONDON

Harry Potter (film franchise, 2001-11) £10.4m

Notting Hill (film, 1999) £19.5m

Sherlock (TV series, 2010-present) £10.8m

YSTAD (SWEDEN)

Wallander £17.9m

Kyuss mig (film, 2011) £32, 100

Maria Larssons eviga ögonblick (film, 2008) £205, 000

APULIA (ITALY)

Braccialetti rossi (TV series, 2014) £6.9m

Che bella giornata (film, 2011) £860, 000

Mine vaganti (film, 2010) £1.3m

MALTA

Game of Thrones (TV series, 2011) £1m

Gladiator (film, 2000) £860, 000

Popeye (film, 1980) £9.6m

The research was commissioned by EuroScreen, an INTERREG IVC-funded initiative which seeks to capitalise on the major economic and cultural opportunities afforded by 'screen tourism'; this being people visiting a country, city or location which they have seen in feature films or on television.

The research was conducted by social media intelligence agency Human Digital, who processed comments and interactions across sites including Twitter, Facebook, Reddit and Pinterest.

Their research examined activity relating to the four European locations along with a range of films and television shows linked to these places.

Their analysis found a clear correlation between place and screen, with the resulting 'chatter' - likes, mentions, retweets - equivalent to paid-for advertising ranging from tens of thousands to millions of pounds. It is believed to be the first time such methodology has been applied to the tourist industry.

The research was announced at the Seen on Screen: Capitalising on Screen Tourism conference in London.