The incident happened on on the Northern Line between Leicester Square and Waterloo. (Jack Taylor/Getty Images)

A gay porn star has pleaded guilty after filming a threesome on a London Underground train, allegedly before other passengers.

George Mason, whose gay porn name is “HungYoungBrit,” and his boyfriend Nicholas Mullan, 24, recorded a video of them engaging in sexual activity on the tube on February 19 last year.

The video, which can still be found online, shows the men having anal and oral sex as they travelled three stops on the Northern Line from Leicester Square to London Waterloo.

Gay porn star George Mason and boyfriend plead guilty to filming threesome on tube

A third man was involved in the video, but his face was pixelated and so officers have been unable to identify him.

“Complete on live sex at front of general public on subway train!,” reads the description for the video.

“And there are lots of normal members of people watching in disbelief

“Genuine naughty brit lads suck n f*ck uncooked and don’t.”

Mason and Mullan pleaded guilty to one charge of outraging public decency at Westminster Magistrates Court on Friday, reports The Sun.

Outraging public decency is punishable with an unlimited prison sentence or unlimited fine under the criminal law offence in England and Wales.

According to The Sun, prosecutor Victoria Murphy told the court: “On the 19th of February 2018, British Transport Police were contacted to a report of a video which had been posted online showing three men engaged in explicit sexual acts on a train.

“It showed full sex, oral sex and masturbation in the presence of the travelling members of the public.”

Police unable to identify third man in gay porn tube video, court hears

Murphy explained that a man, who is gay, saw the porn video online and reported it to police because he thought it “overstepped the mark and was morally unacceptable.”

Mason, 35, previously spoke to the BBC about his so-called “chav porn” in a June 2017 interview.

“I’m a chav,” he told the BBC.

“And I’m proud to be who I am. When I think of other gay guys fetishising me, I feel empowered by that. People are fantasising about me because of who I am.”

Out Down Under is growing daily with over 50,000 followers spread out across our social media and is the leading Australian LGBT News and Events pages. If you would like to advertise in these news stories or have banner ads on our home page then please send us a message via Facebook for our rates.

For more Out Down Under LGBT Australian News and Events please Like us on Facebook and Follow Us on Instagram