There are set to be fireworks this week, not just in the night sky, but the court room.

More than two years after it was revealed he'd been overpaid superannuation, lawyers for Deputy Prime Minister Winston Peters say they're set to explain how the error happened.

Peters will tomorrow take the stand to give evidence in a privacy lawsuit he's bringing against former National Government ministers Anne Tolley and Paula Bennett, the Ministry of Social Development, the chief of the public sector watchdog, and a top civil servant.

Since 2017, the New Zealand First leader's argued he was the victim of dirty politics when media were told he'd paid back seven years of superannuation overpayments.

National has consistently denied being behind the leaks, as has the Public Service.

Otago University electoral law expert Professor Andrew Geddis told the Weekend Collective there's no doubt Peter's annoyed.

"Basically he's going after everyone he could possible do in the hope he will finally get someone."

He says that there may be some public good out of the legal action. 

"Why it might actually matter is that the Government holds a huge information. If that information can be fed on to ministers and used whenever ministers find it politically useful to do so, that's a little bit worrying."

Over the next three weeks, politicians, officials and journalists will front the High Court to figure out whether Peters was wronged - and if so by whom.