The Harman Undertaking, also known as the Harman Obligation, is not found in legislation, but in the UK case of Harman v Secretary of State for Home Department [1983].
It is an implied obligation not to use documents obtained or produced as a result of the compulsory processes of the court for any collateral or ulterior purpose.
The High Court of Australia in Hearne v Street (2008) has described this as a substantive and implied obligation. In Hearne v Street, the court held that:
‘Where one party to litigation is compelled, either by reason of a rule of court, or by reason of a specific order of the court, or otherwise, to disclose documents or information, the party obtaining the disclosure cannot, without the leave of the court, use it for any purpose other than that for which it was given unless it is received into evidence.’
A Harman release case:
http://www.austlii.edu.au/au/cases/cth/FedCFamC2F/2022/840.html
I’ve set up a go fund me campaign to fight the bankruptcy proceedings my ex has launched against me: https://gofund.me/24af5893