The Washington Post this week carried a headline about a country that “is not just squashing the curve – it’s flattening it”. The country in question is not the United States, not the UK, Italy, Germany or Japan, all of which continue to cope with large numbers of cases and deaths. It is New Zealand. At the time of writing, they have had just over a thousand cases of Covid-19, and four deaths. Leadership matters in a crisis, and New Zealand’s leader, prime minister Jacinda Ardern, can surely take considerable credit for this thus far hugely impressive outcome.

Of course, New Zealand is a smaller country than the UK or Australia, let alone giants like the US and China. But the principles in leading a country of 5 million through a crisis are the same as leading a country with 50 or 500 million. You have to lead. You have to devise, execute and narrate a strategy. You have to set out difficult choices, make difficult decisions, take the country into your confidence about why you are making them. You have to show genuine empathy for the difficulties your people are facing, and take them with you.

On all of those, Ardern scores highly. New York governor Andrew Cuomo has rightly won plaudits for his crisis management, and especially his communications. But if you add the outcome of that single-figure death toll in New Zealand to the public performance of leadership, Ardern is surely one of, if not the, standout leaders of this crisis.

It was a conversation with a friend in New Zealand that prompted me to study Ardern’s recent statements, briefings, interviews and social media posts. They are a masterclass in crisis communications. He told me: “If there was an election tomorrow, Jacinda would win every seat. She has put the whole country in strict lockdown, and because of the way she has conducted herself, and explained it, approval ratings for her and the policy are through the roof.”

In a recent piece setting out principles of crisis management learned the hard way alongside Tony Blair through Kosovo, 9/11, Afghanistan, Iraq and, closer to home, a foot and mouth epidemic and the fuel protests of 2000, I emphasised the need to “get the big moments right”. On the Covid-19 crisis, the two biggest moments for Jacinda Ardern came two days apart.

On 21 March, when Boris Johnson was still resisting a lockdown for the UK, and he and US president Donald Trump had been sending all manner of mixed messages about handshakes, big gatherings, science, schools, and much else besides, she did a broadcast to the nation spelling out the strategy for New Zealand. In this rugby-obsessed nation, unsurprisingly, one of the central messages sounded like something from an All Blacks team talk: “We go hard, we go early.”

She emphasised the need for firm action to stop the spread of the virus during what she called “the window of opportunity” before it really took hold, as had happened in China, Iran and, at the time she was speaking, in Italy and New York. She set out, and explained in detail, but in clear, simple language, the four stages of Alert, and what each would require of government and of people. Her manner was calm, authoritative, and friendly.

She focused on the human as much as the economic consequences of the changes that would come as the country went through the different Alert gears. She spelled out very clearly how difficult it would be for everyone. She didn’t say “don’t panic buy”. Instead, she explained, smiling, how the supermarkets, pharmacies and petrol stations would function, and stay open. She spoke to New Zealanders’ sense of themselves – “creative, practical, country-minded” – and she ended by urging everyone to “be strong, be kind, and unite against Covid-19”.

Two days later, moving from Alert level 2 to 3, giving the country a further two days to prepare for the lockdown of Alert level 4, she delivered this memorable line, which helped frame both government action and the public’s understanding of it: “We only have 102 cases – but so did Italy once.”

Admitting she was demanding “the most significant restriction of movement in modern history”, she set out how schools, bars, restaurants, cafes, pools, playgrounds and all non-essential businesses would close. She said without it New Zealand could see “the greatest loss of life in our history” and she was not prepared to let that happen. Perhaps with the Mother Country, the UK, and the US in mind, she said other countries had chosen not to “go early, go hard”, and she was clearly not making the same mistake.

She gave immediate clarity sadly lacking in the UK about who key workers were, and what essential journeys were. In urging people to “stay home, save lives”, she thanked them in advance, portraying what they would do as an act of public service almost on a par with those on the healthcare frontline. She spelled out how the government would do both contact tracing, and testing, and insisted that the more rigorous they were on all fronts, the likelier it was the lockdown could be lifted earlier. “We will do everything to protect you; I’m asking you to do all you can to protect all of us,” she added, with a Kennedy-esque touch.

“Be strong and be kind,” she repeated, smiling, before taking many questions from the media, smiling again when she was asked if she was scared. “No,” she said. “Because we have a plan.”

She shared that plan in a way I have never felt the US and UK governments have shared theirs, which has allowed an impression to develop that they are rather making it up as they go along.

Natural empathy has always been a strong point for Ardern. We saw it in her handling of the massacre of 50 Muslims in a Christchurch mosque last March. She did not just get the words and the tone right, not least vowing never to utter the now forgotten name of the murderer, but she got the actions right too, promising gun law reforms within 10 days, and delivering them in six.

At the other end of the empathetic scale, could any other leader have stood at a government lectern as she did recently and talked directly to children about how yes, the tooth fairy and the Easter bunny were key workers, but they might not be able to get everywhere because they were so busy in these challenging times?

Locked away at home for 23 hours a day, I spend many of those hours studying different world leaders as they deal with the Covid-19 challenge. Ardern is the only one who seems to be smiling as much in the crisis as she does in what might be termed normal times. It seems to help her, and New Zealand, get through it.