Seeing the smiles on families faces was something the Pike River Recovery Agency had worked so hard for in the past 16 months.
Yesterday, for the first time in eight-and-a-half-years, three men opened the entrance tunnel to the mine and entered Pike River.
Pike River Recovery Agency CEO Dinghy Patterson told TVNZ1's Breakfast today the mission went "like clock-work" after an attempt a few weeks ago was called off at the last minute because of unexpected gas levels in the drift.
"It was a fantastic day, I was just so happy to see the smiles on the families faces and that's what everybody at the agency here has worked so hard for for that last 16 months," Mr Patterson said.
On November 19, 2010, 29 men went to work at the coal mine and never came home after a deadly explosion underground, almost certainly as a result of corporate and regulatory failure.
Pike River Family Reference Group member Anna Osborne, who lost her husband in the explosion, told 1 NEWS yesterday, "This is the start of a journey that will end with truth and justice."
And Mr Patterson agreed. Believing in the possibility of full re-entry, he left a note up the drift which said "we will be back".
"A lot of people have believed this is possible, and a lot of people over the past eight years have fought really hard for it, and that credit has got to go to the families."
In order for re-entry yesterday, methane was taken out of the tunnel and replaced with nitrogen. Then yesterday before entering, fresh air was pumped in 180 metres up the drift.
The gas levels are constantly being monitored to make sure they are safe. Unexpected readings were what halted re-entering the mine three weeks ago.
"Yesterday just went like clock-work, it went all according to plan," Mr Patterson said.
"There's a lot of people involved in what we do, so there'll be three groups go in a group at a time."
The first group does a hazard assessment of the area and look for anything of immediate interest, the second forensic group will then go in and do a thorough check 20 metres at a time with police outside guiding them, then the third group will go in and advance all the mining services forward ready for the team to start again the next day.
"We're expecting that any evidence will be found up the top of the drift, but even things like [Pike River mine disaster survivor] Russell Smith's loader halfway up the tunnel, we'll be bringing that out and that alone will be quite a big job," Mr Patterson said.
"That load has been sitting there for eight years but we will bring it outside, we have to."
The work is expected to take five months to complete.