The BBC's lawyers argue in the latest filing that Trump's family members had "personal knowledge" of his intentions in delivering the speech, making their testimony and documents relevant to the president's defamation claim. Drawing on evidence previously gathered by a US congressional committee, the filing says Donald Trump Jr and Ivanka Trump were present when their father revised and delivered his speech, adding that Jared Kushner drafted a proposed statement for him that would have condemned the use of violence.

The filing asks the court to allow the subpoenas to be served by email and certified mail, saying attempts to serve them by hand were unsuccessful. A subpoena is an order for someone to answer questions under oath or provide evidence.

Failure to comply results in a penalty. In one instance, according to the document, a representative for the BBC's legal team tried to deliver a subpoena for Ivanka Trump and Jared Kushner at their home in Florida, but was refused entry at a police checkpoint and was later told by the Secret Service that the agency could not accept the subpoenas.

Similarly, according to the filing, a representative tried to serve a subpoena for Donald Trump Jr at Trump Tower in New York but was told by the concierge that the person who normally took such documents may have been at lunch. During another attempt two days later, the representative was told the "legal department" was not in that day, according to the filing.

President Trump's legal team has been approached for comment. The BBC press office declined to comment.

Last December, Trump sued the BBC and subsidiaries BBC Studios Productions and BBC Studios Distribution over the 2024 Panorama episode. Trump's lawsuit - filed in Florida - accuses the BBC of "intentionally, maliciously and deceptively doctoring" the speech he gave outside the Capitol on 6 January 2021.

However, the BBC has asked the court to dismiss the lawsuit, arguing that the programme did not meet the legal criteria for defamation and was not made available on its US platforms. com, BBC Select or through US broadcasters.

Earlier this month, the judge in the case granted Trump's request for a delay in him handing over financial documents to the broadcaster as part of the suit. The BBC has asked for some of Trump's financial records in relation to his argument that the documentary damaged the president's business interests.