A SELF-proclaimed teen assassin exchanged sexually explicit messages with an A.I. chatbot before he set out to kill Queen Elizabeth II, a court heard.

And Jaswant Singh Chail was encouraged by his artificial intelligence girlfriend Sarai before he got into Windsor Castle’s grounds with a crossbow on Christmas Day in 2021, the Old Bailey was told.

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He had formed an emotional and sexual relationship with the bot as he shared 5,280 messages with it via the app Replika.

Chail was also obsessed with Star Wars and referred to himself as “Sith” and “Darth Jones” in a video he made inside the royal estate.

He was said to be motivated by the films’ ideology concerned with destroying old empires.

When arrested, Chail — who sent the video to his twin sister and 20 others — told police: “I am here to kill the Queen.”

Prosecutor Alison Morgan KC told the court former supermarket worker Chail, of Southampton, knew the difference between fantasy and reality despite his obsessions.

Psychiatrist Dr Nigel Blackwood said that even though Chail had retreated from the world, he had still “followed through a carefully conceived plan without difficulty”.

He told the Old Bailey he was “not struck by any evidence of psychosis or descent into psychosis” and added: “None of this speaks to me about a loss of contact with reality.”

Chail, now 21 but 19 at the time of the incidents, admits an offence under the Treason Act, making a threat to kill the then Queen and having a loaded crossbow in a public place.

More evidence of his mental state will be heard before he is sentenced.