Prince Harry made a surprise appearance in London on Monday.

The Duke of Sussex, 38, attended the High Court for the first day of a legal case in which he and other prominent figures including Elton John, Elizabeth Hurley and Jude Law's ex-wife Sadie Frost are suing Associated Newspapers Ltd (ANL), publisher of the Daily Mail and Mail on Sunday, for illegal information gathering.

Dressed in a dark suit, white shirt and tie, Prince Harry watched intently during the proceedings, sometimes taking notes, from his seat two rows behind the leading lawyers in the case. Frost also sat nearby, and John arrived at the High Court later in the day.

The four-day hearing will consider legal arguments from both sides and will conclude with a judge's ruling on whether the case should go to trial. Associated Newspapers are arguing that the case should be thrown out.

It is the first time Prince Harry has been in the U.K. since the funeral of his grandmother Queen Elizabeth in September. PEOPLE understands that he jetted into London to show his support for the case and informed both his father King Charles, 74, and brother Prince William, 40, that he would be in the U.K. and attending the proceedings.

Harry will likely not see William while he is in the U.K., however, as the Prince of Wales is currently taking some time off with his wife Kate Middleton, 41, as their three children — Prince George, 9, Princess Charlotte, 7, and Prince Louis, 4 — are on a school break.

Jordan Pettitt/PA Images via Getty Images Prince Harry

It is not expected that he will see his father King Charles, 74, either. The British monarch was due to be in France at the beginning of his now-postponed tour. The King and Queen Camilla, 75, will leave for Germany on Wednesday instead.

When it was announced in October 2022, Harry's lawyers claimed that he was among seven individuals who had "become aware of compelling and highly distressing evidence that they have been the victims of abhorrent criminal activity and gross breaches of privacy by Associated Newspapers."

James Veysey/Shutterstock Elton John

The claimants alleged in their lawsuit that unlawful practices included the placement of listening devices in their cars and homes by private investigators, the surreptitious recording of private telephone calls, the payment of police "with corrupt links to private investigators" for sensitive information, impersonation to obtain medical information from hospitals and care facilities and illicit manipulation into accessing bank accounts, credit histories and other financial transactions.

Associated Newspapers deny the allegations, calling them "preposterous smears," the BBC reported.

Justin Ng / Avalon Prince Harry on March 27

The other claimants in the case are John's husband David Furnish, Baroness Doreen Lawrence, who is the mother of race-attack victim Stephen Lawrence and Sir Simon Hughes, a leading Liberal Party politician and former U.K. government minister.

Justin Ng / Avalon

The lawsuit is just one of a number of cases that the Duke of Sussex is involved in against British newspaper groups. Prince Harry is also undertaking a separate libel lawsuit against Associated Newspapers centering on a Mail on Sunday article about the royal's legal ba