The Duke of Sussex and six other prominent figures await a High Court decision on the substantial legal costs they may have to pay to the Daily Mail's publisher following their unsuccessful lawsuit.

Among those involved are Baroness Doreen Lawrence and Sir Elton John, who had accused Associated Newspapers Limited (ANL) of unlawful information-gathering.

ANL vehemently denied the allegations, leading to an 11-week trial in London earlier this year, where Mr Justice Nicklin dismissed all claims on 7 July.

The High Court reconvened this week for a two-day hearing to determine costs, revealing that ANL's total expenses exceed £34 million.

At the end of the hearing on Thursday, Mr Justice Nicklin said he would give his decision on the size of an initial payment the group will make to ANL, as well as how the costs will be assessed, in a written ruling next month.

The judge described the size of the costs in the claims as “unprecedented” for a High Court media law case.

ANL, which also publishes The Mail on Sunday, has asked for more than £9.9 million as an interim payment ahead of future hearings to decide its legal costs in depth.

Antony White KC, for the publisher, said in written submissions that there was “no dispute that Associated is entitled to payments on account of its costs” from the group of household names, with the court later told this would be a “global” figure which could be split between the group.

Lawyers for the group of household names, also including David Furnish, Sadie Frost, Liz Hurley and Sir Simon Hughes, said the interim payment should be just over £7.9 million.

Nicolas Bacon KC, for the group, said in written submissions that the level of interim payment sought by ANL was “manifestly excessive”.

He said: “Associated’s estimated costs have been subject to significant reduction whenever they have been considered by the court, and have been reduced by over half on every occasion that such costs have been judicially considered.”

Mr Justice Nicklin said the claimants would need to pay the interim payment on August 28, adding: “They are going to be paying a sum of money that I will confirm in the judgment.”

During the hearing, lawyers for ANL said the group of household names should pay on an indemnity rather than a standard basis, which would be more favourable to ANL in terms of the amount they can recover.

Mr White said the legal claims were brought for a “collateral purpose” of trying to pressure the Government into introducing the second stage of the Leveson Inquiry, describing it as “a campaign rather than ordinary and reasonable litigation”.

However, speaking on behalf of Sir Simon on Thursday, Mr Bacon said the former MP’s claim was “limited”, adding: “He wishes to make it clear through me that he was not a campaigner against Associated.

“He made no public statements adverse to Associated or its employees.”

Mr Bacon later said in written submissions that it could be “very significant” if the group of seven had to pay ANL’s costs on this stricter basis and could lead to them being without enough insurance cover.

He said that on the standard basis, a judge will need a good reason to award more costs than were set out in court-approved budgets, but this does not apply when costs are awarded on an indemnity basis.

Mr Bacon said ANL’s incurred costs as of earlier this month were nearly £34.5 million, which “exceed its approved budget” by more than £18.6 million.

The barrister added that the group of household names has obtained insurance cover of a combined £16.2 million.

He continued: “If the claimants were required to pay Associated’s costs on the indemnity basis, however, the current level of cover would be insufficient to meet their total costs exposure, possibly to the tune of many millions of pounds.”

Mr Justice Nicklin is expected to give his written ruling in the week of August 17.