Prime parts of inner-city Auckland, including land freed up by the Newmarket Viaduct replacement, will be offered back to the original family trust that originally owned them in the 1840s.

A High Court in Auckland decision, released on Tuesday, gave a potted history of the prominent Dilworth family.

James Dilworth arrived in New Zealand from Ireland and by the time of his death in 1894, owned significant tracts of Auckland land.

The Dilworth School, in Epsom, was established by his will and opened in 1906.

Over the years, some of the Dilworth property has been taken under the Public Works Act, including several parcels of land underneath the Newmarket Viaduct, built in the 1960s, which carries the Southern Motorway into central Auckland.

Following the recent replacement of the viaduct, the Dilworth Trust Board, which owns the land under Newmarket's Westfield shopping centre, wanted large parts of the original holdings offered back.

The parcels are in the area bordered by Broadway, Mahuru St and St Mark's Road.

The court judgement of Justice Rebecca Ellis says NZ Transport Agency was reluctant to sell the land back as the strategically important viaduct would inevitably undergo major renovations works in 50 years' time.

"It is possible that the land would be exempt from the offerback obligation because there had been a significant change in character as a result of the public work," she said.

However, while NZTA had the right to procure the land in the future, if required, to construct or repair the motorway, the "largely unneeded" land should be offered back, Justice Ellis said.

"In my assessment, Dilworth has succeeded more than it has failed [in its offerback plea]."