World Indoor Championships: Lina and Laviai Nielsen on 4x400m dream

"People talk about having to travel a rocky road with lots of highs and lows but I feel like we've climbed mountains to be where we are."

Lina Nielsen and twin sister Laviai have dreamt of representing their country together on the same relay team almost since they ran laps around the primary school playground.

It should have been so simple. Selected to make their senior British debuts together as part of Britain's 4x400m team for the 2017 European Indoor Championships, their hopes were dashed when Lina was forced to withdraw with a stress fracture in her foot.

It took another five years for them to be picked together again in the relay at the 2022 World Championships, only for Lina to suffer a severe relapse of the multiple sclerosis that afflicts both sisters but which they had kept secret to that point.

The Nielsens hope this weekend will prove third time lucky. Barring further misfortune of illness or injury, the sisters will be the leading lights in Britain's 4x400m team at Glasgow's World Indoor Championships.

A medal for the British quartet is a firm possibility. Finally, a twin ambition 27 years in the making could reach its culmination.

"There have been so many setbacks along the way," says Lina, who belatedly made her senior international debut in 2022 after switching to the 400m hurdles as her primary individual event.

"It's the nature of sport - it is cut-throat. Sometimes you need luck on your side. Hopefully we're all good this time round. It can't get better than finally racing together in front of a home crowd."

It has already been an unexpectedly joyous winter for the twins. The pair moved to Aarhus, Denmark, in October to train under former British Athletics coach Tony Lester, who is now employed by the Danish athletics federation.

Under a new training regime, they planned to treat the indoor season as a brief opportunity to test out their fitness before an Olympic summer. But, with the World Indoor Championships not originally on their agenda, results prompted a hasty change of heart.

Both sisters have taken close to a second off their indoor 400m personal bests, with Laviai's mark of 51.11 seconds placing her fifth in the rankings for the Glasgow event.

Instructed by Lester that "third is not an option", their most recent outing saw them deliver a historic 400m one-two at the British Championships, where Laviai triumphed.

"It's crazy how this indoor season has panned out," says Laviai, sitting next to her sister on a video call from their Aarhus apartment. "We were training pretty hard until the end of January and had no idea what shape we were in.

"I didn't plan to go all the way through the indoor season, because the 400m in the UK is so competitive, my main focus is on Olympic trials outdoors this summer.

"After I ran 51.1, I was sitting on a plane back to Denmark thinking 'I don't know if I'm making the right decision'. Every fibre of my being was telling me to go to the World Indoors.

"We still think I can go a lot faster so I don't want to shy away from the possibility of a medal."

Their achievement is all the more notable given they live with neurological auto-immune disease multiple sclerosis.

Diagnosed aged 13, Lina had kept the condition under control before a sudden flare-up on the eve of her World Championship debut in 2022 that prompted her to reveal her story publicly.

Laviai also has the disease but is yet to suffer major symptoms.

"We're still deciding not to take medicine because we're not sure of the side effects," explains Laviai.

"We've always been pretty good with our diet and nutrition, but after Lina's flare-up we've taken it even more seriously. So far it's all gone well."

This weekend's World Indoor Championships remain part of their bigger picture.

Laviai hopes to make the 400m final that would stand her in good stead for an Olympic tilt this summer in Paris, where Lina aims to compete over 400m hurdles and join her sister in the 4x400m.

If they do stand on the relay podium together for the first time in Glasgow, Laviai says it will be a moment they have waited for their entire lives.

"We would definitely celebrate it greatly," she says. "It would be huge."