Winston Peters returns to Wellington as battle over his leaked superannuation overpayment continues

Winston Peters was back in Wellington on Tuesday, just metres away from Parliament.

But it wasn't to announce a return to politics, instead to continue his years-long battle to get to the bottom of who leaked his superannuation details. 

Back in the capital, Peters refused to talk about himself. 

"Why don't you run along and make something else more useful with your life," he told Newshub with a grin. 

Asked if it's the end of New Zealand First, Peters said: "It's probably the end of you. I don't know why you're wasting my time."

As for who could be his successor, Peters replied: "How boring."

Peters was in Wellington attempting to overturn the High Court's dismissal of his case over who leaked details of his superannuation overpayment.

His counsel admitted they may never know who did it.

They argued the Ministry of Social Development boss at the time breached Peters' privacy by alerting a National Party minister under the no-surprises policy.

"The more people who know the greater the risk of this tiger escaping," Peters' lawyer Brian Henry said in court. 

Peters' case for appeal hinges on whether the court agrees that personal details shouldn't be shared under that no-surprises policy, unless there's suspicion of fraud. 

"All they're doing - in our submission - is providing to a minister salacious information," Henry said. 

The Crown's lawyer Victoria Casey QC said, "With respect, he doesn't know what he's talking about."

The Crown questioned why they didn't bring it up during the 2019 trial. 

"To plead a case that this was salacious gossip and political senior career civil servants playing dirty politics at a high level failed... it wasn't even run in the High Court," said Casey.

The hearing is set down for one more day. But Peters will have to wait longer for the judges' decision on his appeal.

And New Zealand will also have to wait to learn whether he'll have another crack at getting back into Parliament.