This, with additional elevation from the height of the towers, gave a stable and efficient antenna, better than ship-based stations, ensuring coverage of southern England with only a 10 kilowatt transmitter.
[citation needed] The third season finale episode of Patrick McGoohan's Danger Man (known in the U.S. as Secret Agent) called "Not So Jolly Roger"[2] was filmed on Red Sands Fort in early 1966, when Radio 390 was broadcasting (a year before it shut down).
The episode, first broadcast on 7 April of the same year, concerned a pirate radio station that was a front for spies passing on secrets, and included substantial scenes filmed on location at the fort.
Following Radio Caroline's launch, other pirate broadcasters sought to establish themselves in the Thames estuary by gaining access to abandoned World War II anti-aircraft forts, which were more cost-effective than purchasing ships.
[5] As a result, some suspected foul play in the Radio Invicta deaths,[7] but this was never proved;[3] questions were also raised about the seaworthiness of the David, and the coroner's inquiry returned an open verdict.
[6] This was also short-lived,[8] officially closing down on 22 September 1965; however, it continued to broadcast a repeated announcement which advised listeners to retune to 390 metres MW in order to direct them to the new Radio 390 station.
[6] On 25 November 1966, after a magistrate's court case lasting two days, Radio 390's management was found guilty of illegal broadcasting, fined £100 and ordered to close the station.