Lahar survivor and his 'hero' tackle mount

William Pike lost a leg in the eruption. Photo / Doug Sherring

The mother of a mountaineer who lost a leg during a lahar eruption on Mt Ruapehu has spoken of her pride at her son's brave return to the summit yesterday.

Auckland schoolteacher William Pike, 27, and fellow eruption survivor James Christie, 26, accompanied 10 students from Taupo's Hilltop School back to the crater lake where the pair nearly lost their lives.

"It's a huge day for William, particularly as James is going back there with him," William's mum Tracy said. "Without James, he wouldn't be doing this. My husband Barry and I are just so in awe of them both."

The two climbers were sleeping inside Dome Shelter when the mountain erupted in September 2007.

Heavy mud, lake water and flying boulders swamped the hut, trapping Pike and crushing his leg. Christie was later awarded the New Zealand Bravery Medal for saving his friend. He had walked an hour to alert emergency services.

Pike had his right leg amputated after being airlifted to Waikato Hospital.

Tracy Pike insisted her boy "never had a negative moment" during his long and painful recovery.

She hadn't been sure whether he would be able to make it all the way to the summit because his remaining leg still isn't back to full strength - but yesterday, he got there.

Tracy believed the schoolkids on the climb - nicknamed Pikelets - were spurring him on. "William is very fit, swims four times a week and does a lot of bush walking, but this is a real test for him. He joked beforehand that James can carry the load for him and he'll just go up with just his poles."

A large piece of volcanic rock believed to have struck William has pride of place in her Forrest Hill garden.