Anyway... on your marks...

A heads up, the US team has a gent named Wilbert London III.

So posh he has a butler carry the baton for him. Or so legend has it...

The Great Britain quartet:

Rabah Yousif

Zoey Clarke

Emily Diamond

Martyn Rooney

Rivals include Jamaica, United States and Poland, who as I have already described, have mixed up their order.

Andrew Cotter
BBC Sport commentator in Doha

You can choose which order you put the athletes out in. Every country has gone man, woman, woman, man, except for Poland, who have put their two men out first to put them into a good position.

The 4x400m mixed relay is about to kick off on the track and Great Britain have a team seeking a medal.

However, we are hearing that Poland have decided to mix up their order meaning we will get to see their men facing women and their women facing men.

So here we go, we have a battle of the sexes without a tennis ball in sight.

Now then. Get ready for some carnage...

Saj Chowdhury
BBC Sport in Doha

So I managed to get myself to a special IAAF exhibition at a mall conveniently located five minutes from where I am staying. You don't want to be walking much in 40C.

They had memorabilia from the great and good including, Allyson Felix, Usain Bolt, Mo Farah and... Seb Coe, the former Olympic champ, who is the IAAF president, as you all know. He probably curated the whole thing.

If anything it was great collection of vintage footwear.

Image source, BBC Sport

Image source, BBC Sport

Image source, BBC Sport

BBC Sport

Great Britain's 800m runner Kyle Langford believes he was threatening a top-two finish before being blocked by rivals as he finished fifth in his semi-final to miss out on progressing.

Asked if he felt it severely damaged his chances he says: "One million percent. I was closing quicker than anyone in the home straight.

"People are cutting in on on one another. I felt like I still had my legs. They have ruined the racing. You want to keep it clean but I should have raced better and kept out of that danger. It was a slow race and maybe I should have taken it on myself. Emotions are high now and I don't know what to think."

Katerina Stefanidi misses her second attempt at 4.95m by a couple of centimetres.

She'll be heading back with the bronze medal.

The first miss of the night for Sandi Morris - but not by much!

She all but clears 4.95m but a little touch from her collar as she goes over wobbles that bar.

Anzhelika Sidorova also misses her first attempt at it. She's so inscrutable compared to Morris, barely a flicker showing on her face whether it goes wrong or right.

Great Britain's final 800m men's hope is Kyle Langford, who almost got a medal two years ago in London.

He's off and running in his semi-final and they ease through halfway in 53.07. Only two will make it through automatically here. Fastest losers have no chance at this pace. Langford makes a move on the back straight and others respond.

He gets cut up by a rival and loses momentum. To the final bend, Amel Tuka leads, Langford trying from far back but there is too much traffic.

Tuka takes it on 1:45.63 from American Bryce Hoppel on 1:45.95.

Image source, .

My WORD.

Sandi Morris, at the first attempt, absolutely sails over 4.90m. She made that look so easy! Morris lets out a fist pump and a scream, gesturing at herself and the crowd to come on.

Image source, .

But...

"Anything you can do, I can do better," says Anzhelika Sidorova, as she too goes flying over 4.90m with ease.

Katerina Stefanidi passes another attempt at 4.90, and the bar shifts up to 4.95m.

It's the early stages of the men's triple jump final and American Will Claye - seeking his first global outdoor gold - has the early advantage after leaping to 17.72m in the second round.

Big rival and defending champion Christian Taylor fouled with his first attempt.

And Holly Bradshaw just can't do it!

It would have been a British record and it's a fine attempt from Bradshaw, but her knees tipple the bar, and she will finish in fourth place.

So, so close...

Off and running in semi-final number two of the men's 800m.

Emmanuel Kipkurui Korir of Kenya and Donovan Brazier of the US are big medal hopes.

A 52.13 first lap, well down on the first semi-final. Britain's Jamie Webb in fifth and working hard.

Brazier looks strong as his arms drive him up the home straight, Marco Arop of Canada under pressure from Korir. Arop holds him off to take second.

A 1:44.87 from Brazier and 1:45.07 from Arop. Not as quick as semi-final number one but those two are safely through. Jamie Webb clocked 1:48.44 for Great Britain.

We're down to the last four.

America's Sandi Morris and Russia's Anzhelika Sidorova, competing as a neutral athlete, are tied for the gold medal. Katerina Stefanidi of Greece is third and Holly Bradshaw is fourth.

Here she goes, one shot at 4.90m...

Well.

Holly Bradshaw has got her jumper on - she's passed at 4.85m, which means she'll have one bash at 4.90m.

Wow.

Scratch that!

On her second attempt, Katerine Stefanidi goes sailing over the bar, and the Greek champion pushes Holly Bradshaw down into fourth place.

Here she goes...

Knees pumping, she plants the pole - and her feet just knock the bar over! She's still tied in third position with Katerina Stefanidi.

American Donovan Brazier is in semi-final number two for the 800m. He's clocked 1:42.70 this season so you can see how Great Britain's Jamie Webb will have a lot to do given his PB of 1:44.52.

A big ask.

On your marks...