Tom Fordyce
Chief sports writer in Rio

Wayde Van Niekerk might just have achieved the impossible twice - detonating a record many considered untouchable, maybe overshadowing Usain Bolt on his biggest night of all. And doing it all from lane eight...

Kirani James took silver in 43.76, LaShawn Merritt third in 43.85.

Wayde van Niekerk absolutely streaking out in lane eight...

Away! Kirani James streaking away in green, LaShawn Merritt giving chase...

I think we could get a fast time here. Three great runners with nothing between them. Though Wayde van Niekerk has ended up in lane eight which is a bit of an issue for the world champ. 

The British 400m record could go here. Iwan Thomas set the mark of 44.37 way back in 1997, but Matt Hudson-Smith ran 44.48 in the semi to make tonight's big race.

All set?

Up next - the men'd 400m final. One of the ultimate athletic events in my eyes, for no real reason.

Michael Johnson, Roger Black, Kriss Akabusi, legends everywhere during the 1990s.

Now it's Kirani James, Lashawn Merritt and Wayde van Niekerk going for gold. 

Early days in the qualifying round of the high jump but Great Britain's Chris Baker has just cleared 2.26m - the only competitor so far to do so.

Baker's compatriot Robert Grabarz has cleared the 2.22m mark so far.

Image source, AP

David Beaumont: Absolutely quality run from Laura Muir. Looked class. She has a medal chance if she runs like that in the final.

Simon Smith: What a great run from Laura Muir, how comfortable was that???

Sam Holloway: Lovely stuff from Laura Muir. That's going to be another final to watch!

Colombian Caterine Ibarguen is in the lead in the women's triple jump.

Ibarguen, 32, who went on a 34-meeting unbeaten run after finishing second in London in 2012, leaped 15.03m in her second jump.

American Michael Johnson stormed to both 200m and 400m Olympic titles in front of a home crowd at Atlanta in 1996.

Relive those races, which prompted BBC commentator David Coleman to utter the memorable line 'this man is surely not human'.

The men's 100m final may take the headlines overnight but the men's 400m could end up being an even better race.

The top three contenders - LaShawn Merritt, Kirani James and Wayde van Niekerk - have all clocked 44.11 secs or faster this year.

Rapido.

Image source, Getty Images

Justin Gatlin and Yohan Blake qualify for 100m final, while Great Britain's James Dasaolu finishes sixth

Tom Fordyce
Chief sports writer in Rio

Hugely impressive 1500m qualification from Britain's Laura Muir, responding perfectly to a brutal last lap of 57.59 secs from Dibaba. She remains a real possibility for a medal in Monday night's final.

Genzebe Dibaba won that semi, Sifan Hassan second, and Laura Muir third.

Muir for a medal? She is in the conversation...

Laura Muir matches a kick from Genzebe Dibaba down the back straight, this is impressive stuff. She crosses the line in third place and easily qualifies. Well ran!