Secrets of Great British Castles is a British history documentary series that grew from the success of Irish TV series Tales of Irish Castles. The idea - initially created and written by Billy McGrath - was rejected by state broadcaster RTE. It was subsequently pitched to Ben Frow - the director of programming for Ireland's 1st ever commercial channel TV3 - and it proved a ratings success. When he returned to London to head up Channel 5 Ben asked Billy (then partner in Sideline Productions) to expand on a new idea based on UK castles. The result was the much more ambitious Secrets of Great British Castles produced by Dublin based Sideline in 12 parts. It was first broadcast between 3 April 2015 and 9 December 2016 (6 parts per season). Historian Dan Jones came on board as host and writer to explore the history behind Great Britain's most famous castles and is currently broadcast on Netflix around the globe. International sales for SoGBC were secured by DCD Rights and the deal for Sideline was negotiated by ICM Partners London (now CAA).