In secular New Zealand, the beach is not just a pleasant recreational space. It is a kind of vast sacred site - film set, wild museum, lovers' lane and escape route from claustrophobic suburbia. Probably not one family in a thousand has Christmas dinner on the beach under a pohutukawa tree, but everyone thinks they do, or at least that they will next year.
The fear that all this was to be lost, and delivered by the courts into Maori ownership, caused a furore that threatened Helen Clark's Labour government and is reshaping the constitutional landscape.
The panic started when a group of South Island Maori, aggrieved that they were being locked out of lucrative aquaculture deals (mainly mussel farming), took their case to court. The appeal court judges decided that the claimants may well have certain rights over the foreshore and seabed, and that they were entitled to have them tested in a lower court.
The government gave the appearance of panic: it would not allow any claims to proceed to litigation, it said. The beaches must be kept in public ownership of some kind. This angered the Maori, who argued that they were being denied their common-law right to go to the courts. It also excited a wild surmise that the Maori did in fact own everything. Tribes immediately claimed title to sand, shore, sea and seabed out to the 200-mile limit.
Then Don Brash, the colourless ex-banker who leads the opposition National Party, stepped in. Brash spoke of "a dangerous drift towards racial separatism". The Maori - backward-looking, permanently aggrieved, over-dependent and at the same time overpowerful - were being given "a birthright to the upper hand".
The blame for this, he said, lay squarely with the Treaty of Waitangi, or rather, with its newly acquired prominence. Signed in 1840, the treaty was the nation's founding document, promising equality to the Maori. Thoroughly breached by the colonists, then neglected for a hundred years, it was revived in the 1980s as a kind of "living document" defining the partnership between government and the Maori. Since then it has become the basis for a number of large compensation payments (of which Brash approved), but also a few (very few) affirmative-action programmes. It has also led to mandatory consultation with the Maori who had thus, said Brash, acquired disproportionate power. "One rule for all" and a single standard of citizenship, were Brash's demands.
Overnight, the National Party shot up 17 points in the polls and it has continued to climb, reaching 49 per cent late last month. (It has dipped slightly since.) Sorely rattled, the government promised to re-examine the constitutional status of the treaty. This further upset the Maori, for whom Waitangi has led to a revival of morale and culture, and a steady (in some cases spectacular) improvement in education, health and income. The Maori also noted the flaw in Brash's argument: "one rule for all" does not apply when Maori property rights are at issue.
But his speech struck a deep chord. Even some of his natural foes feel queasy about a constitutional arrangement that makes most citizens "subjects" of the Crown, while the Maori minority (16 per cent) are "partners" of the Crown, with ever-fluctuating demands for special rights and exemptions.
The revival of Maori language and culture has at times taken on a menacing aspect for many whites, who feel like strangers in the land - literally, because the new, politically correct term for whites is tauiwi, a word whose meaning hovers between "aliens" and "fly-by-nights".
Whether he intended them to or not, Brash's comments have darkened the political and social atmosphere. Right-wing MPs feel emboldened to fling racist abuse ("blackfella!") at a government minister or to describe one large Maori community as a "cesspit". Meanwhile, listeners to Maori radio are informed that the Maori live like blacks under apartheid, or Iraqis under the Americans, and may even hear praise for the "military option used by the IRA". One Maori politician, popular with both communities, warns of civil war if the National Party wins office.
The puzzle is why it all started in the first place. The offending court of appeal judgment was in fact exceptionally cautious. It stressed the formidable difficulties of proof facing Maori claimants to any proprietary interests in the coasts, and warned the lower Maori land court that its decisions would be subject to appeals, in which the general public's interests would be considered. In other words, the spectre of Maori freehold title to the coasts was just that - a spectre - all along.
So why did the government not just play down the appeal court judgment? The answer possibly lies in the word "aquaculture". Like other maritime nations, New Zealand is on the brink of a huge boom in marine farming.
Using technology developed for deep-sea oil drilling, "ocean ranching" will generate billions of dollars of income, and the New Zealand government, like that of the US, is already planning, and perhaps already negotiating, leases to farm the ocean. Maori claims to ownership would horribly complicate matters and could go winding through the courts for years. When the court delivered its judgment, it must have seemed tempting to ministers to use white fears as an excuse to shut off the road to litigation.
Given the general secrecy of commercial treaty-making, it is impossible to prove the truth of this theory, but either way, the government badly underestimated the passions involved.
Peter Walker's book on New Zealand, The Fox Boy: the story of an abducted child, is published by Bloomsbury