Auckland City Missioner Diane Robertson said an enormous amount of work went into the lunch.
"It would be impossible for us to make a success of this special lunch, and all the other activities, without the generous support of the volunteers," she said.
"At the Mission, we believe no one should have to eat alone on Christmas Day.
"It is not about poverty, it is about the spirit of Christmas, and about celebrating with each other."
Mr Coffey, 40, and about 20 volunteers will this morning complete much of the preparations for the meal, adding final touches tomorrow.
Giant ovens at the Viaduct Events Centre were used, and the food was kept warm until tomorrow's lunch.
Doors open at 11.30am and the Mission expects to host about 2500 guests.
Mr Coffey, who was a chef and now works for the NZ Defence Force college, has helped out at six lunches, and said the other volunteers were the key to the event running so smoothly.
"It's just a good feeling, and there's a good bunch of volunteers, it definitely makes the day a lot easier," he said.
His dedication is all the more impressive for the fact he doesn't wait around for a plate of leftovers - there's one more meal to get started on, albeit a tad smaller.
"I finish a little bit early, because I then have to go home and then cook Christmas lunch for my family. So I usually don't hang around for my lunch."
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