Prince Harry, Elton John Arrive to Court for Associated Newspapers Lawsuit

Prince Harry has made the trek to England, but not to make peace with his family ... he's there to wage war with a media org, and Elton John is joining him on the front lines.

The Duke of Sussex arrived Monday at London's High Court ... flashing a smile as he went inside to begin legal proceedings in his ongoing lawsuit against Associated Newspapers, which distributes The DailyMail and other UK tabloids.

He wasn't the only one there ... the Rocket Man himself was on hand. Harry and Elton have company ... EJ's husband, David Furnish, actress Sadie Frost, Baroness Doreen Lawrence and Elizabeth Hurley. SF showed face as well on Monday, joining in the lawsuit.

Harry has already taken Associated Newspapers to court with his wife, Meghan Markle, and settled.

This time around ... Harry and the gang claim the publisher violated privacy laws, including allegedly bugging their cars and homes, tapping their phones, paying off cops for inside info, among other damning accusations that they say have crossed the line big time.

Associated Newspapers has denied the allegations ... so now, everyone's gonna make some preliminary arguments in front of a judge to see if this case can move forward.

Harry's already involved in a separate legal case with these folks. In addition to what Meghan sued them over a couple years back, he's sued them again for libel over articles they ran about his security arrangements.

The battle goes on.