The Duke of Sussex is due to appear at the High Court as his case against the publisher of the Daily Mirror over alleged unlawful information gathering begins.

Harry is suing Mirror Group Newspapers (MGN) for damages, claiming journalists at its titles – which also include the Sunday Mirror and Sunday People – were linked to methods including phone hacking, so-called “blagging” or gaining information by deception and use of private investigators for unlawful activities.

His claim is being heard alongside three other “representative” claims during a trial which began last month and is due to last six to seven weeks.

Harry alleges about 140 articles published between 1996 and 2010 contained information gathered using unlawful methods, and 33 of these have been selected to be considered at the trial.

MGN is contesting the claims and has either denied or not admitted each of them. The publisher also argues some of the claimants have brought their legal action too late.

The duke is due to arrive at the court in London on Monday and is due to enter the witness box on Tuesday, when he will face cross-examination from MGN’s lawyers.

His court appearance comes just over a month after he attended the coronation of his father the King.

It is thought to be the first time a senior member of the royal family has personally appeared in court proceedings since 2002, when the Princess Royal pleaded guilty to a charge under the Dangerous Dogs Act after her pet bit two children in Windsor Great Park.

On the first day of the trial, lawyers for MGN said the publisher “unreservedly apologises” to the duke for one instance of unlawful information gathering and that it accepts he was entitled to “appropriate compensation”.

Andrew Green KC said it was admitted that a private investigator was instructed, by an MGN journalist at The People, to unlawfully gather information about Harry’s activities at the Chinawhite nightclub one night in February 2004.

“Otherwise, the specified allegations are denied, or in a few cases not admitted,” he added.

Mr Green said there was a reference to a payment record for £75 in February 2004.

He continued: “It is admitted that this represented an instruction to engage in unlawful information gathering, and MGN unreservedly apologises and accepts that the Duke of Sussex is entitled to appropriate compensation for it.

“MGN does not know what information this related to, although it clearly had some connection with his conduct at the nightclub.”

The barrister said that there was a People article published in February 2004 “giving the recollection of a woman Harry spent time with” at the club.

Mr Green added: “The Duke of Sussex notably does not claim in relation to this article, so it is not alleged that this instruction led to the publication of his private information.

“The fee paid, £75, suggests little work was involved.”

The three other representative claimants are Coronation Street actor Michael Turner – known professionally as Michael Le Vell – who is best known for playing Kevin Webster in the long-running soap, former Coronation Street actress Nikki Sanderson, and comedian Paul Whitehouse’s ex-wife Fiona Wightman.

Mr Green said voicemail interception was denied in all four cases and that there was “no evidence or no sufficient evidence”.

The barrister continued: “There is some evidence of the instruction of third parties to engage in other types of unlawful information gathering in respect of each of the claimants, save for Mr Turner whose claim is entirely denied, and MGN has made pleaded admissions in respect thereof.

“MGN unreservedly apologises for all such instances of unlawful information gathering, and assures the claimants that such conduct will never be repeated.”

At the start of the case, an MGN spokesperson said: “Where historical wrongdoing has taken place we have made admissions, take full responsibility and apologise unreservedly, but we will vigorously defend against allegations of wrongdoing where our journalists acted lawfully.”

MGN has previously settled a number of claims against it in relation to unlawful information gathering, but a 2015 trial of representative claims, including those brought by former Coronation Street actress Shobna Gulati, ex-footballer Paul Gascoigne and actress Sadie Frost, is the only other trial to have taken place during the long-running litigation.

Harry previously attended the High Court in March to attend a preliminary hearing in his separate claim against Associated Newspapers Limited (ANL) – the publisher of the Daily Mail and Mail On Sunday.

A ruling is awaited in that and in another case brought by the duke against ANL, over Mail On Sunday coverage of his claim against the Home Office about his security arrangements when in the UK.

He is also bringing legal action against News Group Newspapers, publisher of The Sun and the now-defunct News Of The World, over unlawful information at its titles and is awaiting a decision on whether that claim can go ahead to a trial expected in January next year.

The duke is due to conclude his evidence on Tuesday, and witnesses for MGN relating to Harry’s claim are due to be called to give evidence on Wednesday, although the schedule may change.