Eighteen months ago, he was untroubled as he drove down Auckland's Southern Motorway in his navy Bentley Continental.
Stopping off to visit his planned $1 billion 40,000-house estate in South Auckland, the Irish migrant who once washed dishes to pay for food spoke of his ideas.
Flat Bush would be the first new town to be built as a proper town centre in New Zealand since World War II, a genuine hub and quite unlike anything attempted before, he said.
But before he got to the paddocks of Flat Bush, he said he was not just confining himself to Auckland but working at two Central Otago projects - Kawarau Falls and the $500 million McArthur Ridge - as well as Atlantic City in the United States.
That was December 2007, when Mr McKenna was leaping from one giant project to the next.
This is a migrant made good.
In the mid-1980s he left Ireland for Wellington.
The son of an Irish builder, he grew up in a London terraced house but his family moved to the Irish countryside when he was 10.
He developed a love of construction, because his father ran a small building firm employing half a dozen tradesmen.
His father died when McKenna was 20 and the young man worked at a series of menial jobs, such as washing dishes and pumping petrol, to help pay the family bills.
In last year's NBR Rich List, Mr McKenna's fortune was estimated at $100 million.
Many people praise him for the risks he has taken and the influence he has had as perhaps New Zealand's most prominent property developer of the past decade.
John Duthie, Auckland City Council city development general manager, credits Mr McKenna's Auckland waterfront vision with transforming that vast area, starting from the Quays and Sebel near Kermadec restaurant at the city end, then moving down to the huge Lighter Quay apartment blocks and Westin Hotel nearer Westhaven.
Mr McKenna had added considerably to the city, Mr Duthie said.
Others to praise him include former ING Property Trust executive Andy Evans, for his real estate abilities, and Rodney Walshe, honorary Irish consul-general, for his business acumen.
Although Mr McKenna initially comes across as quietly spoken and somewhat reticent, this disguises a steel backbone and iron will, Mr Walshe says.
He praises his generosity and community contribution.
Mr McKenna has also been praised for bringing a hotel of the quality of Westin to New Zealand and is renowned in property circles for his good taste and interest in design and interior decor.
