It was more or less business as usual for Labour MPs at their annual caucus retreat in Martinborough this afternoon, with one noticeable big red exemption.

Blocking the picturesque rolling hills and vineyard was a sizable, inflatable bouncy slide.
Prime Minister Jacinda Ardern was clear to her MPs and to the curious press gallery members – some quite keen for a slide: "It's only for children".

She told the Herald that she had not had a turn, and did not intend to either.

Labour MPs' families often accompany MPs on the retreat, which is quite child-friendly.

But it is understood this was the first time a bouncy slide has ever been brought along to the retreat.

The Herald can also confirm no taxpayer funding was used to pay for the slide.

Labour MPs were in good spirits throughout the day, most ditching usual Parliament work clothes for short-sleeve shirts, shorts and skirts.

Ardern joked with one reporter that he was too formal and playfully stole his pocket square, before returning it moments later.

Wielding a plastic bat, Immigration Minister Iain Lees-Galloway, right, hits it for six, while Wairarapa MP Kieran McAnulty watches. Photo / Jason Walls

While waiting for Ardern's 1:30 stand-up, an impromptu game of back-yard cricket broke out between some MPs and reporters.

Wielding a plastic bat, Wairarapa MP Kieran McAnulty squared up against an on-form Immigration Minister Iain Lees-Galloway, who was bowling at pace.

McAnulty was dismissed before the Prime Minister began her media stand-up.

Labour MPs will stay at the retreat for one more night, before heading to Ratana tomorrow.