The lost mass grave from the country's first major battlefield has been uncovered in Northland.

The 12 British soldiers lay for more than 170 years after the Battle of Ruapekapeka.

Photo: Alexander Turnbull Library / nzhistory.net.nz

They died on 11 January 1846 during the attack on Ruapekapeka Pā.

Archaeologist Jono Carpenter made the remarkable discovery of their missing graves at the battlefield, near Kawakawa.

He has spent years in search of the graves and has been working to uncover the identities of the men.

Photo: Supplied

Ngāpuhi kaumatua were at the site as Mr Carpenter carefully lifted the soil to reveal the soldiers' remains - a significant find both locally and internationally.

"It's a missing war grave from the last battle of the first of the New Zealand Wars," he said.

"In the international context, frontier conflicts leave dead bodies behind but they're very, very hard to find. So internationally I think this is significant."

Mr Carpenter said the emotion, or wairua, was evident as the soil was carefully brushed from the remains of the lost men.

Photo: Supplied

"I just felt hugely, hugely honoured and hugely grateful to the people who let the work go ahead.

"I think the most amazing part of this story is that it was the descendants of the people who fought at Ruapekapeka, built Ruapekapeka and faced the British over the bush and the gullies who really kept the story of this lost grave alive.

"This belongs to the Whanaunga of Ruapekapeka who have embraced the memory of these men, the enemy of their ancestors."

Photo: RNZ / Shannon Haunui-Thompson

Allan Halliday from the Ruapekapeka Trust and a descendant of one of the battle chiefs, Hare Paraha, said he was honoured to be present for the duration of the excavation.

He said a musket ball was found underneath the ribs of one of the men.

"This is probably how that soldier died - he got shot in the puku and he had a pipe with him, a clay pipe. And we felt that was his, it had laid with him since 1846 so even though it would have been good to take it and put it in a museum on display its kind of like, it's his."

Photo: Supplied

Like many others, Ngāti Hine chairman Pita Tipene has connections to both sides of the Ruapekapeka battle.

Although his ancestor are Te Ruki Kawiti and Mataroria, he also descends from Lieutenant Colonel Robert Wynard who led the 58th regiment at the battle.

"It's really tinged with sadness but it's also exciting because finally we can put to rest where these people were buried, because up until this point the very spot where they were buried wasn't marked and as a result people have grown food on top of them, cows have been roaming.

"Due respect and reverence needs to be put to these men who were very brave and galant in their time."

A memorial or a tohu maumahara is being planned to mark the soldier's grave.

Watch The Stories of Ruapekapeka, a documentary highlighting Northland's most infamous armed conflict, hosted by RNZ's Māori Issues Correspondent Mihingarangi Forbes, and made alongside Great Southern Television with funding from NZ on Air.