The Kiwi nurse who UK Prime Minister Boris Johnson hailed as keeping him alive has shared what it was like to be at his bedside and thanked New Zealanders and Prime Minister Jacinda Ardern for their messages.

Invercargill-born Jenny McGee was singled out by Johnson as one of the nurses integral to his recovery from Covid-19.

McGee was visiting family back home in New Zealand in February, but told TVNZ that she felt such a sense of duty that she returned to London as the coronavirus pandemic escalated overseas.

"It was totally out of the blue," she said of Johnson's public message of praise.

McGee kept vigil at the Prime Minister's bedside for two days as he lay in intensive care.

"We were constantly observing, we're constantly monitoring," she said.

When asked if she was nervous to be attending the PM, McGee said she'd been working in intensive care for ten years, had been a Sister for five years.

"I've been in really stressful situations and I was not fazed by this."

Johnson received no special treatment different to other patients at the NHS, McGee said.

"We take everyone very seriously that comes into intensive care. These patients who come into us, it's a very scary thing for them, so we don't take it lightly.

• Parents of kiwi nurse who helped Boris Johnson enormously proud

"He absolutely needed to be there."

The 55-year-old spent a week at St Thomas' hospital, three of those nights in an intensive care unit.

McGee said the PM was interested to know about her hometown - Invercargill - and they spoke about New Zealand.

The toughest part of that time was the speculation about Johnson's health, she said.

"There was a lot of media interest in him being in hospital, and to be honest, that's probably the toughest thing of the lot."

Prime Minister Jacinda Ardern, who messaged the nurse following Johnson's praise, was "a hero" of McGee, she said.

"She said how proud she was of me and the country was so proud. It's so heartwarming and something I'll never forget."

She even had "a bit of banter with Ardern, she said. "I responded and she messaged back immediately. Again, surreal, a couple of emojis".

But her newfound fame has led to some teasing from her NHS colleagues.

"I'm getting a lot of stick from my workmates, I'm loving it," she said.

"There are kids telling me they want to be a nurse, there are families saying how proud they are and it means so much right now. People will never know how much it means."

"But thank you."

Britain's Prime Minister Boris Johnson speaks from 10 Downing Street praising NHS staff in a video message, after he was discharged from hospital. Photo / AP

McGee and another nurse - Luis from Portugal, were the reason that "in the end, my body did start to get enough oxygen", Johnson said after he was discharged.

"Because for every second of the night they were watching and they were thinking and they were caring and making the interventions I needed," he said.

"So that is how I also know that across this country, 24 hours a day, for every second of every hour, there are hundreds of thousands of NHS staff who are acting with the same care and thought and precision as Jenny and Luis."

The 55-year-old was admitted into St Thomas' with persistent coronavirus symptoms on April 5, but was moved to intensive care the next day as his condition worsened.

Johnson spent three nights in intensive care, where he was given oxygen but was not on a ventilator.

He's now recovering at his Chequers country residence.

But McGee, 35, hasn't spoken to media until today - she's been back at work at the intensive care department at St Thomas' Hospital in the city.

She's been flooded with messages of thanks and support following Johnson's post, even receiving a Facebook message from Prime Minister Jacinda Ardern.

Her brother Rob McGee told the Herald she'd made her family proud.

"We are all very proud of Jen, not just in the support she gave Boris - but what she has been doing helping everyday people," he said.

"She just saw it as another day and kept just saying she is just doing her job.

"Whilst she is blown away by Boris' recognition, she is just really pleased to see the public recognition for the amazing work the NHS is doing - that made her really proud."

Father Mike said she didn't crave the publicity that came with her hard work.

She said 'Dad I was just doing my job, I was nursing him just like I was nursing any patient who came through the door'."

"When you're an intensive care nurse you are nursing one on one with the patient. You are right there all the time, tending to their every need basically, monitoring all the machines," Mike McGee said.

"These people she is dealing with every day are seriously, seriously ill. And it's her job to try and get them well again and get them out of the hospital."

Raised in Edendale, Southland McGee rose up through the ranks to become Senior Sister after a some years at the Royal Melbourne Hospital and St Thomas'.

Although some New Zealanders have been forced to return home because of stricter visa conditions in the UK, her hospital vouched for her and helped her stay in the country.

As the pandemic spread to the UK, it because clear she would be on the frontline.

"There was a worry about how she would protect herself," Mike said. "And she said 'Look, I'll be ok, it's more you oldies back home, make sure you look after yourself'.

"Jenny just seems to have that knack of being able to keep everybody calm and support them and let them know the medical people are doing the very best they can for their loved one."

The United Kingdom now has more than 133,000 confirmed cases of Covid-19 and recorded at least 18,100 deaths.