The UK should note that when the going for our produce got tough in the 70s, we behaved diplomatically.

There are two certainties about next week's referendum in Britain on whether to leave the European Union. One is that, whatever the result, it will leave a nation deeply divided. The other is that, should Brexit win, the British will be confused politically and commercially about what to do next.

Will Britain have to begin two-year negotiations as mandated by the Treaty of Lisbon drawn up specially for any nation wanting to leave the EU?

Will Britain start trying to establish new bilateral trade agreements?

And where does New Zealand come in on all this?

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Our farmers suffered when Britain joined the European Economic Community in 1973. Access for our agricultural products to our most important market was virtually shut down. The British rated the bright prospects of being in a united Europe far ahead of their presumed loyalty to their former colonies.

No matter what the result of the referendum, so much has changed in New Zealand's international trade relations since that crisis of the 1970s. We now have a Trans-Pacific Partnership that John Key tells us is a wonderful achievement though many conundrums have yet to be unravelled. We are negotiating with 15 other nations a Regional Comprehensive Economic Partnership trade deal.

In October last year New Zealand and the EU agreed to begin working on a comprehensive free trade agreement. Any new trade deal with the EU, it is hoped and expected, will improve New Zealand's access to the European market - with or without Britain.

The Governor of the Bank of England has warned that Britain would be facing a recession if it voted to leave the EU. Other leaders of international economic organisations have predicted troubles galore if the British quit the EU. So we shouldn't presume Britain would be open for prosperous business if Brexit wins.

Already we can see world markets getting alarmed at the prospect of a British exit and the damage that would do to the European Union. A Brexit win is expected to see a fall not only in the pound but in the New Zealand and Australian dollars.

None of this changes the fact that for New Zealand the priority is to get a more successful free trade agreement with China and to expand relations with Asian nations.

The British referendum could bring back some painful memories of how New Zealand and Australia felt abandoned, in trade terms, a generation ago.

The EEC's common agricultural policy ensured that Europe's farmers had exclusive and protected rights to the European market. The official reason for creating the common agricultural policy was to guarantee food supplies for Europe " particularly in case of war. But it was inspired by the French who wanted not only to defend their farmers but to satisfy their obsession with retaining the charm of rural France.

Looking back to those tumultuous days, one lesson emerges. That is, the way the Kiwis could teach the Aussies how to behave more wisely in international affairs.

Britain's ban on access to its markets was more severe on Australia than it was for New Zealand. Australian political leaders were furious and displayed their anger in regular missions to EEC headquarters in Brussels and in London.

While I was in the Australian embassy in Brussels two Prime Ministers, Gough Whitlam and Malcolm Fraser, and John Howard, who became PM a few years later, came to demand a better deal for Australia from the insular European Commissioners. They all claimed they'd pressured these EEC bureaucrats to acknowledge the Australian case and Fraser was able to get a commitment for regular meetings intended to improve relations. But Europe's market remained closed.

The EEC's agriculture minister, John Silkin, gave me a different version of the way these Australian protests were delivered. He told me he'd been disappointed at the reticence, in fact refusal, of Australians to seek Britain's help in the campaign against the excesses of the common agricultural policy.

In contrast New Zealanders were much more resourceful and co-operative. According to Silkin, he was a source of information about what was going on in the EEC's Council of Ministers and he was able to present a convincing New Zealand case for better treatment. This paid results at first, he said, when NZ was given short-term trade access to some European markets.

European Commission president Roy Jenkins told officials he'd never had to deal with such rude, vulgar and aggressive people as the Australians. An even more forceful expression of Britain's frustration with the Australian campaign came from the head of the European Commission external relations directorate, Sir Roy Denman.

He told me in Brussels: "Your f****ing Australian ministers like to kick the arse of the commission to get cheers from a thousand cattle farmers."

I asked Sir Roy if Australia would have got a better deal if it had been more sophisticated and diplomatic. He evaded a direct answer but pointed to New Zealand's success in getting access for its butter and lamb "without kicking anyone's arse". Diplomacy can take many shapes and forms when the going gets tough. The going will get very tough and not only for the British if they decide to get out of the EU.

Vincent Matthews was First Secretary (Information) in the Australian Embassy in Brussels from 1974 to 1978.