Southwark-resident Mason, who shares his name with an 18th-century US constitutionalist, was slapped with a £1,000 penalty after admitting to outraging public decency. Belfast-native Mullan was ordered to pay £170 in costs and serve a 12-month community order.
"The two men in the dock engaged in various sexual acts" on the Tube "in the presence of the travelling public," Prosecutor Robert Simpson said.
"The incident is recorded by them and the video of what happened was subsequently uploaded on to Twitter, where another gay man saw it, thought that had crossed the line of what was acceptable behaviour and the incident was reported to the police."
"During the course of the journey, the idea came about that they would have sexual relations on the train," Mr. Cohen said.
But Lucinda Lubbock, who was chairing the bench at the time, said that the act was "unpleasant and serious," adding that "the way it took place back in July, the seriousness of the offence, is exacerbated by the fact that it went on social media."
"We feel that this is a lesson to both of you", Ms Lubbock said. "As your defence lawyer said, you have been humiliated in the court of social media."
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The incident took place in July 2017 but had not been reported to the British Transport Police until 19 February of last year after a tweet entitled "100% genuine footage" circulated the amorous threesome engaging in the sexual act whilst riding on the Northern Line of the London Underground.