We've had the first casualty in the high jump final - Puerto Rica's Luis Castro Rivera has failed his three attempts at 2.24m.

Still early stages, but Mutaz Essa Barshim is looking as good as ever.

Andrew Cotter
BBC Sport commentator in Doha

That was a shocking performance from Germany. They're the world's fastest team this year.

It's a season's best for Great Britain. Safely done.

Jamaica win that heat in 42.11, Daryll Neita motoring on on her final leg to secure second for the Brits (42.25).

China third. Germany, surprisingly, are fifth.

GB right back in there at the second and third changeovers. A brilliant third leg from Ashleigh Nelson.

A great start from Jamaica, and from China too. GB struggling at the changover but Lansiquot on her way.

Second heat under way. Asha Philip with the GB baton first up.

GB are in lane four. Jamaica in lane eight.

GB are in action in the next heat, and have chosen to rest Dina Asher-Smith for this race. A wise decision, given her achievements this week.

Jamaica are also involved in this one - they've got a certain Shelly-Ann Fraser-Pryce among their line-up. She will run the second leg.

Colin Jackson
Two-time world 110m hurdles champion on BBC TV in Doha

The United States did what they had to do. They were a little bit scrappy at the beginning.

At the second change everything went haywire for all the teams. It was very messy.

Australia were all over the place in that. A fall and they don't finish. A lot of tears now from them.

Kiara Parker flies away to bring home the win for the USA. A messy start from them but they pulled it back in the end.

Trinidad and Tobago finish second in a season's best with Switzerland third.

At the second changover, the USA and Trinidad and Tobago are looking good.

It's the USA with the edge though.

First heat up and running - literally.

Two heats. First three per heat go through to the final plus the next two fastest teams. Simples.

In the first heat are the USA - the reigning world and Olympic champions. They are in lane three.

How do they line up? Like this.

1. Dezerea Bryant 2. Teahna Daniels 3. Morolake Akinosun 4. Kiara Parker

Next up on the track it's the women's 4x100m relay heats.

A reminder of the British team - Asha Philip, Imani-Lari Lansiquot, Ashleigh Nelson and Daryll Neita.

The British men's quartet has also been announced - Adam Gemili, Zharnel Hughes, Richard Kilty and Nethaneel Mitchell-Blake. They race from 19:05 BST.

Massive cheers for defending champ Mutaz Essa Barshim as he gets ready for his first jump, and he's up and over 2.19m in the blink of an eye.

We're still in the early stages, but everyone bar America's Jeron Robinson cleared the opening height at the first attempt.

Saj Chowdhury
BBC Sport in Doha

The Scottish 1500m boys are on fire. Off the top of my head I don't remember the last time there were three British men in a major global final of the event... Coe, Ovett and Cram in Los Angeles? Or am I going back too far?

The time for the second heat was similar to the first - any one of Neil Gourley, Josh Kerr and Jake Wightman could get a medal. IMO.

Josh Kerr and Jake Wightman have just both spoken to BBC TV after reaching the men's 1500m final:

Kerr: "In those scrappy races, we were running pretty fast. I am really happy with how I performed, I got a clear run at it and that's all I needed to do."

Asked about three Scots getting through, he added: "It's fantastic, we've had a clean sweep in the British Championships in the last couple of years and it's time for us to show up on the biggest stage."

Wightman: "I still don't believe it - there's the 'Q' on the big screen! I made hard of work of that but it bodes well for the final that we all got through."

Meanwhile, over in the high jump, Mutaz Essa Barshim is a big deal...

Image source, EPA