London was a whirlwind two days of meetings with politicians and financial experts before flying off to Washington DC to hobnob with American economic bigwigs. He still has good contacts from his days as Reserve Bank Governor, he says.
Of course Brash was sorry to miss New Zealand's big moment and, as if to prove his loyalty to the ABs, he sports an All Blacks jersey when we meet the evening he arrives in London, at his hotel in posh Belgravia.
As we leave the lobby to head out for dinner, Brash asks if I think it is okay he isn't wearing a jacket and tie, displaying that same touching boyishness that saw him, years ago, admit he lived on a diet of corned beef and peas at one stage.
Showing few signs of jet lag after the long-haul flight in premium economy (he paid his own way - hence no business class) the 71-year-old is upbeat and chatty, keen to discuss the rugby.
He is much better company than the awkward, gaffe-prone figure that sticks in the memory from his days as National Party leader.
In fact, he's a cheery and old-school chivalrous type, helping me with my coat and insisting on walking me the short distance to the tube station after dinner. The chirpiness continues while we wait a few minutes outside the Sardinian restaurant for it to open for our early booking.
He looks momentarily glum after answering his mobile, the New Zealand caller informing him about a "scathing" newspaper editorial.
But the only time his good humour really fades is when I mention his estranged wife, Je Lan. He was spotted at a Kiri Te Kanawa concert with her just before leaving for London.
The pair separated nearly four years ago amid accusations of infidelity on his part, and Brash has been open about trying to win back his wife's affections in the years since.
Just over a month ago he told the Herald on Sunday the pair had been dining together frequently, but over dinner he politely declines to discuss the Kiri concert, saying Je Lan is sensitive about it and he's been "a bit too open" about airing his feelings.
He's working hard on not being single forever but Brash admits he likes living in his bachelor pad in central Auckland within walking distance to several favourite eateries.
Knowing his penchant for junk food - the meeting with Rodney Hide that led to Brash replacing him as Act leader was at Burger King, on Brash's suggestion - I was mildly concerned about taking him to a Sardinian restaurant. I needn't have worried. He tucks into his veal escalope with relish and finishes off with a bitter honey gelato (he's an ice-cream man, apparently).
And he insists on paying for everything, including the glass of red wine each of us had. There's no going Dutch with Don.
As for the corned-beef-and-peas jokes that he can't seem to leave behind, he swears he hasn't touched the stuff in years. It began with a confession in his biography that he ate nothing but corned beef, peas and KFC for three years after splitting with his first wife.
During dinner, Brash is coy about exactly who he's seeing during his two days in London, but the select group was thought to include Bank of England Governor Sir Mervyn King, who recently said the world could be facing the worst financial crisis ever.
That comment was the catalyst that caused Brash to jump on a plane just weeks before the election, at a time when most politicians were door-knocking, sending out press releases and wiping moustaches off their election hoardings.
Terrible timing? Not necessarily, Brash counters, although he was disappointed to miss that game.
"I knew that if we won, the next three or four days would be Cloud 9 and celebrating, and if we lost, it would be utter desolation and mourning," he says. "I figured that win or lose, they weren't going to be interested in what I had to say about the economy."
He may have had a point there, but didn't he want to be seen at the victory parade; try for that crucial photo op with Richie McCaw? Not appropriate, says Brash. "It looks a bit corny, quite frankly. It's one thing for the Prime Minister but, for anyone else, it looks very forced, I think."
Nevertheless, at a stage when Act needs to pull out some seriously brilliant campaigning to avoid political oblivion come November 26, the party leader's absence must have raised a few eyebrows.
But Brash shrugs off the suggestion, saying the board and those at the top of the party list were enthusiastic about his trip. And he denies that his relationship with Epsom candidate John Banks has become strained since their public disagreement over Brash's cannabis decriminalisation comments and suggestions Banks was therefore vetting Brash's speeches before he made them.
"There's absolutely no tension at all. John and I have known each other for 30 years. We have as good a relationship as any two politicians I know. We talk every second day; I ring him or he rings me."
He stands by his stance on cannabis law reform but admits regret over the way espousing his personal view has distracted from the Act Party's "key message".
Despite Act currently polling well under the 5 per cent threshold and Banks - who could be Act's only lifeline into Parliament - trailing behind National candidate Paul Goldsmith, Brash is optimistic about his chances.
He describes Act's dismal poll performance as "disappointing", then goes on to say he thinks it "unlikely" he will miss out on a seat in Parliament.
While the polls show that few people want to actually vote for Act, around a quarter want to see the party form some part of the government and/or Brash in a ministerial position. "The challenge is to get them to give us their party vote," Brash says.
So how does he plan on getting people to do that? "Same-old, same-old," he replies. "Billboards, direct mail, speeches, door knocking."
That he may have given his opponents a head start by coming to London doesn't seem to occur to him.
There's no air of desperation about Brash, after ousting Hide and taking party leadership in April this year.
One does have to wonder if he's really that fussed about getting back into Parliament, a lifestyle he describes as "strange".
If it doesn't work out, he says, he'll go back to planting kiwifruit (a long-time hobby; he has an orchard near Auckland and was managing director of the New Zealand Kiwifruit Authority in the 1980s).
So why is he bothering? His raison d'etre - the reason he's flying to the other side of the world: the economy. "I'm really only doing this because I want to make a difference to policy."
