|Spar British Athletics Indoor Championships|
|Venue: Arena Birmingham, Birmingham Date: 9-10 February|
|Coverage: Live on BBC Sport app, on Connected TV and on the BBC Sport website. Catch up via BBC iPlayer.|
At Paris Fashion Week in September, one womenswear brand hit on a gimmick.
Its usual models were unemployed for the evening. Instead famous names from the world of athletics were primped and prepped.
Dina Asher-Smith and Katarina Johnson-Thompson were among those swapping the running track for the catwalk.
Laviai Nielsen, along with her twin sister Lina, are old hands at that sort of thing.
The pair have had modelling contracts alongside their professional athletics careers for several years.
Had Asher-Smith or Johnson-Thompson perhaps dropped either of them a line for some tips?
Nielsen seems taken aback for a half-beat. "I think they just got on with it," she laughs.
"It is not particularly hard, running around a track in less than a minute is much harder."
Laviai certainly did not have it easy last summer.
Coming into the European Championships in Berlin, the 22-year-old was ranked 16th in the continent over 400m.
She had to go through qualifying to make the semi-finals into which British team-mates Anyika Onuora and Amy Allcock had a bye.
But Nielsen shredded the formbook, setting new personal bests in the preliminary round and the semi-finals, before finishing just outside the medals in fourth in the final.
She was as surprised as anyone.
"I had no idea what was going on after winning my semi-final," she remembers.
"I didn't know where I had finished. I didn't know where to look for the results so although everyone else had seen that I had won, I hadn't. I looked up at the big screen and thought, why is the camera on me? Then, finally, I realised."
In two days she had gone nearly half a second faster than she ever had before.
She puts a lot of the credit down to her coach Christine Bowmaker, who represented Great Britain over 100m and 200m at the 1999 World Championships and has overseen her development over the past year.
If Nielsen was shocked by her own performance in the semi-final, Bowmaker supplied another surprise hours before the final.
She had watched Nielsen in the heats, but then flown back to Britain before the semi-final.
"I was having lunch just before my final and Christine called me, asked how I was feeling. She said there was someone outside the hotel to see me, mentioning a journalist who I had met a few days before, and asked would I go outside to chat to him.
"I walked out and there she was standing with my sister. I just burst into tears because I was overwhelmed with emotions on that day.
"I was all over the place, but it was the nicest thing."
Laviai still lives with Lina. The pair have more distinct athletic lives now. They previously competed in the same event under the same coach, an almost indistinguishable twin threat.
Now, Laviai has transferred to Bowmaker's camp while Lina has switched to 400m hurdles.
But Laviai says they depend on each other as much as ever.
"We have both said that if we didn't have each other, we wouldn't be in the sport," she said.
"She is the first person I come to if I have had an especially good or bad race or training session. And she is the same.
"I had a bad session just after Christmas and I didn't need to say anything, she knew as soon as I walked in the door.
"We are different with pre-race nerves, I talk a lot while she gets quite introverted. I think she likes to listen. But we fit together like two puzzle pieces."
This weekend's British Indoor Championships will be a return to the lunch breaks in which the pair would take on all-comers around the athletics tracks in the playground of their Leytonstone primary school.
"Four hundred metres feels like a totally different race indoors. It can get really crowded as everyone comes into lane one at once on the break, you get your elbows out, you are trying not to trip up, and the atmosphere is great because the crowd are so close.
"It brings me back to my days racing 800m. I'll want to get to the front and control it."
With Eilidh Doyle and Zoey Clark - two of her team-mates from Great Britain's 2017 world 4x400m relay silver-medal winning quartet - also in the field, doing so will be no cakewalk. Or catwalk.