The fall of British Prime Minister Boris Johnson coincided with National Party leader Christopher Luxon's arrival in London – and left his dance card short of a few names.

Luxon was due to meet with three government ministers over the past two days in London, but the furore around Johnson meant the meetings were scrapped.

He said he had scheduled meetings with ministers Michael Gove, Nadhim Zahawi and Amanda Milling to talk about housing, education and trade.

However, on the day of his Gove meeting, ministers were resigning en masse and Gove was sacked for disloyalty after telling Johnson to resign.

On the same day, Zahawi was promoted from Education Secretary to Chancellor and Milling – who was meeting Luxon because Trade Minister Liz Truss was out of town – could not make it.

"You can just imagine, you arrive, you literally land, and it was all on, pretty much. It was pretty amazing, you go past Downing Street and you see all the throngs of people outside it. In the UK here it has been an all-consuming 48 hours," Luxon said.

Luxon did meet with former PM Theresa May on the day before Johnson quit and said she was "in good spirits".

Johnson replaced May as Prime Minister after May resigned in 2019 just weeks after a failed no-confidence against her, and under pressure over a failure to deliver on a Brexit deal.

Luxon said he talked to her about politics, cricket and her experience as a former minister for home affairs.

"It was lovely."

Asked if he took any lessons from it, he said it highlighted the effect disunity had in politics, and pointed to his own efforts to resurrect the National Party.

Asked for his thoughts on Johnson, he said it was ultimately a domestic matter for the UK and he had never met Johnson. However, he believed Brexit had been good for New Zealand, noting the UK had managed to secure trade deals in spite of Covid-19.

"Post-Brexit it's been a really positive move for us because we've seen a country that wants to embrace and support free trade around the world and that's a really good thing. They want to engage with the world, and they need to engage with the world and that's been a good thing for New Zealand on balance, I think."

"The bottom line is the UK now needs to do business with as many countries as it can in the world. Those objectives are not that dissimilar to us as a small country that needs to engage with the rest of the world as well.

"So I would hope New Zealand and the UK going forward, irrespective of the government, will be out there in the world trying to build business for their respective countries and with each other."

Luxon said his London visit was not a complete write-off: he had visited the Michaela Community School in London to learn about the charter school model used there, spoken at the think tank The Policy Exchange, and met with the Centre for Policy Studies.

He was also meeting with housing experts and had been to functions with expats in each of the places he visited.

He had lived in London himself for a few years.

London was the final stage of his trip, on which he also went to Singapore and Ireland.

"It's been useful, a really jampacked week with specific objectives in each place. It's good to talk to people who have done things and done things well."

The Leader of the Opposition gets one taxpayer-funded international trip a term and Luxon said it was to help with policy formulation, especially around education and infrastructure.