He said, "On the face of it, it looked like business as usual."
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But Townsend said two "startling and exciting" themes emerged as Key spoke to the audience and answered questions from Property Council members.
He said he was stuck by the similarity between the Prime Minister's vision for Auckland's future and the vision of Len Brown.
Townsend said both leaders were now "completely aligned", both in terms of the need to ramp up supply and the need to build "a little bit up, a little bit out".
He said the Prime Minister delivered a clear message this morning about the future of cities, in particular the need for people to live in apartments.
Key spoke of when he and wife Bronagh bought their first house: "We were in our mid-twenties, we had no kids, and we ate at home once. Who the hell needs a house?"
While Townsend agreed that apartment living was a part of Auckland's future, he said this was a hard message for the public to accept.
He said people got it, but were reluctant to see the apartments built.
"There is opposition from some politicians in Auckland, some local boards and parts of the public as well. But as a nation, New Zealand can no longer afford that opposition. We have to supply."
As for building "a little bit out", Townsend said the Property Council passionately shared Key's view that Auckland must grow outward, building in what are currently semi-rural and rural areas.
Key said it was a certainty that the city's boundaries would spread.
He noted that in his own electorate of Helensville, Kumeu has been designated as a location for several special housing areas.
This will require new infrastructure, to provide for a growing community, said the Prime Minister.
But he added some of the locals wouldn't welcome the move.
"I think that does challenge certain communities."
Key said people want to hold on to their semi-rural living environment, and developments such as this will change the make up of their community.
But he said it comes down to one question: "What are the options?"
"We have to move out and move up, and we have to do a bit of both."
Townsend said, "We know in the next 30 years we're going to have to inject a new city into Auckland, the size of Dunedin...we're going to have to put it somewhere."
He said there was room to move outward in the south and northwest of the Super City, but not a lot.
Townsend also welcomed the Prime Minister's determination to further change the Resource Management Act, despite saying there is zero chance part of the reform will go ahead.
Key said the Government had wanted to merge sections six and seven of the RMA.
But he said the probability of that passing was now "zero".
Townsend said, "Those changes would be desirable, but they're not critical."
He said there was still a huge amount that could be done to tidy up the Act further.
The Prime Minister vowed to make further changes to the RMA.