When Prime Minister Jacinda Ardern meets her embattled British counterpart Theresa May tonight (NZT) she will be hoping the latter will not be too distracted by the Brexit turmoil in her own country to discuss trade.

Ardern, who is in the UK for a brief visit before heading to the World Economic Forum in Davos, Switzerland, has put trade at the top of her agenda, saying free-trade agreements with both Britain and the European Union are priorities.

May is in the midst of the fallout from her defeat in the House of Commons last week over her plan to leave the EU and following her meeting with Ardern at 10 Downing St, May is expected to go back to Parliament to tell MPs how she plans to proceed.

Ardern will be seeking a reassurance from May that New Zealand will be no worse off, including in trade, following Britain's departure from the European Union.

New Zealand Initiative executive director Oliver Hartwich told Kate Hawkesby it's an important chance to discuss our post-Brexit trading relationship.

"It will probably not be Britain's highest priority to settle a trade deal with New Zealand, and they are not really able to do anything at the moment anyway, because they are still trying to figure out what their future relationship with the European Union will be like. But it's probably a good idea to remind the Brits that there are other countries out there who would like to trade with Britain."

Australia has just signed a post-Brexit protection deal, which Hartwich said is similar to what New Zealand should be aiming for.

"There is nothing stopping us from actually progressing talks a bit further. Technically speaking, Britain is not free to enter into really formal trade negotiations until they are freed but, of course, we can pretend that we are in the situation to figure out creatively what might happen once they are out."

Trade negotiations between the countries are historically good, so it is likely New Zealand can secure a deal similar to Australia, he said.

Hartwich said Jacinda Ardern need to discuss what happens in the event of a no-deal Brexit.

"The situation is complicated by the fact that there are some quotas, for example, for agricultural produce from New Zealand for the EU and once Britain splits from the EU, they will have to negotiate how these quotas are split between Britain and the EU."

"So what the Prime Minister should do, is she should try to figure out what happens to these quotas afterwards, because New Zealand shouldn't be worse off after Britain leaves the EU."

Following a morning of talks on the sidelines with other world leaders to push New Zealand's trade agenda, Ardern will meet naturalist and broadcaster Sir David Attenborough on Tuesday afternoon (early Wednesday NZT).

The discussion, which is being livestreamed on the WEF website, will focus on how leaders can take action to safeguard the planet in the face of climate change, pollution and habitat loss.

Ardern will end her first day in Davos attending the chairman's dinner at the Morosani Schweizerhof hotel as a guest of the WEF's founders Klaus and Hilde Schwab.

Ardern is at Davos for two days before heading to Brussels for meetings with European Council and Commission leaders.