Japan make a good start but after the first changeover it's the USA who star.

Vernon Norwood is flying down the track and starts to form a gap between himself and the rest of the pack.

Rabah Yousif is coming around the outside for GB and is in a good place for the changeover.

First heat under way. Cameron Chalmers with the baton for GB.

Great Britain have won three successive bronze medals in this event and so will be expecting to challenge for a podium place again.

Favourites USA (Tyrell Richard, Vernon Norwood, Wilbert London, Nathan Strother) are also in this heat. The USA won silver in London two years ago.

Next up, it's the turn of the men in the 4x400m relay heats. This is how GB line up.

• Cameron Chalmers
• Rabah Yousif
• Lee Thompson
• Martyn Rooney

Image source, British Athletics

Olympic champion Ryan Crouser has got things off to quite the start in the men's shot put final.

First throw. A new championship record of 22.36m.

Casual from the American.

Michael Johnson
Four-time Olympic gold medallist athlete on BBC TV in Doha

Jamaica looked very dominant in the first heat and then you have the US in the second. Great Britain looked good.

I thought it was a good decision to put Jodie Williams on the second leg. They have a good chance of a medal but I think the US and Jamaica will probably take gold and silver.

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

That was a good strong solid performance from Great Britain. They will be very pleased with that.

That's a season's best time for Great Britain, who are all smiles as they huddle at the finish line.

Ukraine take the final automatic qualifying spot with a third-placed finish in 3:26.57.

A lovely run from Laviai Nielsen down the straight, and Great Britain are second!

United States finish first in three minutes 22.95, with GB next in 3:24.99.

Steve Cram
BBC Sport athletics commentator in Doha

Great Britain are looking very good for qualification here.

The United States are the first away after the third change and this is a good run from Jessica Turner, opening up a gap between herself and the rest of the pack.

GB are still second...

The top three from each heat go through and the two fastest losers.

A tidy first changeover for GB and Jodie Williams settles herself in behind Allyson Felix, who is leading the pack.

Zoey Clark, part of the silver-medal winning team in London two years ago, will kick things off for Great Britain in lane three.

Away they go...

BBC Sport

Shara Proctor speaking to BBC Sport: “I’ve been here before, I like to live on the edge. All I focus on is myself and that was enough to qualify.

“It is amazing, it feels bouncy and fast. I just have to contain myself, go home, recuperate and relax before tomorrow.”

GB colleague Abigail Irozuru said: “This is way more nerve-wracking than I thought it would be but it’s my first world championships and first final. Anything can happen (on Sunday) we should all rise to the occasion.”

The teams are lining up but Botswana, who were set to be in lane seven, don't seem to be among them...

Shara Proctor and Abigail Irozuru both qualified for tomorrow's long jump final a little earlier.

Proctor has just described the track as "amazing", saying she couldn't believe how bouncy it was.

Steve Cram
BBC Sport athletics commentator in Doha

Jamaica surely with that showing are going to be contenders.

That was the quickest time in the world this year and it surpasses the time set by the USA's junior team - just to underline their strength.

And in the next heat...

McPherson and Jamaica ease to the win and cross the line in 3:23.64. That's a new world leading time.

Poland second, Canada third.

Jamaica and Poland open up a good gap on the rest of the field and it's a toss up between them who will cross the line first.

But Jamaica's McPherson is kicking on and has moved well ahead of her Polish opponent. Canada have also found another gear and are closing down Poland.