Student digging up past for families of WWI Kiwi Tunnelling Company

During World War I, hundreds of New Zealanders swapped work in coal and gold mines for a scret underground role in France.

On their return, most of the 908 soldiers of the New Zealand Tunnelling Company - the first Kiwis on the Western Front - were reluctant to talk to their loved ones about their time in combat.

But a French PhD student is seeking to uncover their secrets 90 years later so their families can understand what their ancestors went through.

Anthony Byledbal's visit coincides with a gathering of the soldiers' descendants on Monday in Waihi - the first time a gathering has been held to commemorate the men's work.

The Tunnelling Company was created at the request of the British Imperial Government to counteract a German underground attack.

The first contingent of about 400 men left for Britain in December 1915 and, after a month's military training in Falmouth, England, the company were sent to a combat zone northeast of Arras in the Chanteclerc sector for six months.

The tunnellers - helped by 43 members of the NZ (Maori) Pioneer Battalion, the British 184th Royal Engineers Tunnelling Company and English and Scottish infantrymen - tunnelled more than 7km to join up medieval chalk mines and form a 24km network under the two suburbs of Ronville and Saint-Sauveur.

Facilities installed in the quarries, which accommodated 20,000 men, included running water, lighting, kitchens, latrines, a light rail system and a medical centre.

Place names from New Zealand, such as Russell in the north and Bluff in the south, helped the men navigate the maze of underground passages.

About 15,000 troops assembled in the tunnels for the Battle of Arras attack on April 9, 1917.

They broke through to the surface and pushed the German lines back 11km.

Towards the end of the war, the company changed its activities to bridge design and building.

The last tunnellers left France in February 1919. More than 60 of their company were killed, and more than 150 were injured.