The eyes of the media will be turned to the High Court in London this week as the Duke of Sussex gives evidence in his legal action against the publisher of the Mirror.

Harry will enter the witness box amid an ongoing trial over contested allegations of unlawful information gathering by Mirror Group Newspapers (MGN).

Here the PA news agency looks at why the duke is coming to court and what the case is all about:

– What is the legal action against MGN?

The duke and other high-profile individuals are suing the publisher of the Daily Mirror, the Sunday Mirror and Sunday People.

They are seeking compensation over allegations MGN was involved in the unlawful gathering of their personal information for stories.

Claims brought by four individuals, including the duke, are being heard in a civil trial as “representative” cases of the types of allegations facing the publisher, findings over which could affect the outcome of other claims.

– What is unlawful information gathering?

It has been alleged that MGN’s journalists were linked to voicemail interception, colloquially known as phone hacking, securing information through deception and hiring private investigators for unlawful activities.

Lawyers for Harry, whose case covers the period 1995 to 2011, have told the trial that such practices were “habitual and widespread” amid a “flood of illegality”.

– What has MGN said in its defence?

MGN is largely contesting the claims brought against it, but has offered Harry an apology for an instance of unlawful information gathering.

The publisher said it was admitted that a private investigator was instructed by an MGN journalist at The People to gather information about his activities at the Chinawhite nightclub one night in February 2004.

MGN says board members have denied knowledge of unlawful information gathering activities and claims there is “no evidence, or no sufficient evidence, of voicemail interception” in any of the four claims chosen as representative cases – some of which it claims are brought too late.

– What has happened in the trial so far?

The trial, taking place before judge Mr Justice Fancourt, has been focused on witnesses and evidence relating to the “generic” allegations against MGN that feature in claims against it.

Over two and a half weeks, the court has heard from a former MGN chief executive denying involvement in covering up unlawful practices, while an ex-director and former lawyer at the publisher both defended their accounts of when they became aware of such activity.

Ex-private investigators and former MGN journalists have also faced questions over the “dark arts” and “illegal” methods allegedly used to source information, the knowledge of MGN editors and executives and whether certain stories were legitimately obtained.

– Who else is involved in the case?

Former Coronation Street actress Nikki Sanderson, comedian Paul Whitehouse’s ex-wife Fiona Wightman and actor Michael Turner – known professionally as Michael Le Vell – are also having their claims considered as “test cases” at a trial.

All three are also expected to give evidence.

– What is happening in the trial this week?

The trial will focus on the representative claims, beginning with the duke’s.

Harry is expected to be at court on Monday as his lawyers and MGN’s legal team set out their opening arguments on his case.

The duke will then enter the witness box, either on Monday or Tuesday.

– Has the duke been to the High Court before?

Yes. In March, Harry made a surprise appearance at the Royal Courts of Justice in London amid a preliminary hearing in a similar case he is bringing against Associated Newspapers Limited (ANL), publisher of the Daily Mail.

The duke is also suing News Group Newspapers (NGN), publisher of The Sun, over alleged unlawful information gathering, and is bringing a legal challenge against the Home Office in relation to his security arrangements in the UK.

– When will the MGN trial end and when will there be a ruling?

The trial is due to conclude by the end of June with Mr Justice Fancourt expected to give his written ruling later in the year.