Claire Trevett: Recall Ypres, Hollande? Now sign here

Francois Hollande. Photo / AP

So much for the catchphrase "Don't mention the war" - these days no leader in want of a free trade deal should let a historic war go to waste.

For John Key, the G20 was less war and peace than war and pingas. He had said he was going to the G20 to listen and learn rather than advise, but the centenary of World War I meant it was also prime free-trade-agreement-hunting season.

While the world's 19 most powerful leaders were busy bailing up Vladimir Putin and issuing joint statements on Ebola, Islamic State, climate change and the annexation of Ukraine, Key was corralling his free trade targets.

Top of his list were European leaders and the Saudi Arabian Crown Prince - both areas he is desperate to push trade talks with. Key was keen to keep up momentum on a trade deal with the European Union after securing strong support from German Chancellor Angela Merkel last week.

So he secured a meeting yesterday with French President Francois Hollande and emerged saying Hollande was also onside - at least until the sensitive agriculture word was raised. French farmers are notorious for their anxiety over trade agreements - so you can be sure at some point France will be reminded New Zealanders fought and died for France.

It may sound cynical. But it is apparently a legitimate tool of trade diplomacy. The Ministry of Foreign Affairs' post-election briefing stated that the World War I centenary provided an opportunity to develop important international relations and secure better economic gains in Europe and Turkey.

"Our involvement will ensure key partners understand and value NZ's long history of contributing to global peace and security."

That's diplomatic speak for laying on the guilt trip.

The summit proved it can be effective. When Key and South Korean President Park Geun-hye announced the free trade agreement, Park made it clear New Zealand's part in the Korean War was a factor.

Key paid lip service to the most pressing international issues at the summit, but by and large sticking to its economic purpose suited him fine. It was no surprise that when he was asked to deliver an address he was given the topic of trade.

It is partly simply realistic - when you've got the Gargantuas of the world thundering about you, what difference can a mosquito make?

Lest Key have any illusions about his position, the Australian media reminded him - the only mention he got was on the back of the Sunday Mail the morning after the Kiwis beat Australia in the Four Nations. The headline was "We don't want to be rude with Kiwi PM John Key in town, but ... Bugger."

Key, too, admitted the obvious - he was simply a gnat at the G20. At least he knows his place. But anyone could tell him mosquitoes can be very annoying if they apply themselves.