Time for the third - and last - semi-final. Ireland's Thomas Barr runs in lane four. Here we go....

Colin Jackson said beforehand this semi-final was going to be hard to call - and so it proved. Jamaica's Annsert Whyte takes it in 48.32 seconds, with Javier Culson of Puerto Rico joining him as a guaranteed finalist.

Turkey's Yasmani Copello - the surprise European champion - and Rasmus Magi of Estonia face an anxious wait.

Good news for Robbie Grabarz.

He has been awarded his 2.33m jump on appeal.

A few minutes ago he thought he'd cleared the height on his first attempt as the judges white flag went up, but the bar fell a split second later.

Back to the track...do we have a British representative in the men's 400m hurdles final? Afraid not. Jack Green clatters a barrier on the bend, sapping his energy as he goes down the straight. He fades quicker than a dodgy tan, pulling up to cross the line in eighth. Out of eight.

American Kerron Clement wins, with Kenya's Boniface Mucheru in second. They qualify for the final automatically remember.

GB's Eilidh Doyle is into the final as the second-fastest loser.

Take a look at her performance in the semi-final.

Robbie Grabarz isn't happy.

The white flag goes up after his 2.33 jump, but the bar eventually falls. It's a failed jump.

Time to compose and go again.

Image source, BBC Sport

So we know Eilidh Doyle has made the women's 400m hurdles final. But will Team GB be represented in the men's final too? We're about to find out. Jack Green lines up in lane four in the first semi-final...

Denise Lewis
Olympic heptathlon gold medallist on BBC One

Eilidh Doyle didn't put a foot wrong, she took the barriers really well. It was smooth, relaxed and she's made good ground. She really deserved to get through.

Great Britain's Eilidh Doyle reaction to qualifying for the final: "That was close. I'm delighted to get into the final. I apologise to my coach, my husband and my family for putting them through that. Now that I'm in there, hopefully I can do something.

Eilidh Doyle is wearing a big, beaming smile on her face. The reason? She's into the 400m hudles final. Her nervous wait was relatively shortlived as her time of 54.99 is enough for her to go through as the second fastest loser after the third semi-final.

Dalilah Muhammad of the USA and Sara Slott Peterson finish first and second respectively in the third semi to progress.

Russia's only track and field athlete in Rio, Darya Klishina, is currently trying to get through to the long jump final. She's looking good for doing just that, having just cleared 6.64m.

There are also three Brits hoping to progress -  Lorraine Ugen, Jazmin Sawyers and Shara Proctor.

Image source, Reuters

Great Britain's Eilidh Doyle on whether finishing third will be enough to reach the final: "I hope so, I really do. Obviously I would have liked to automatically qualify but I'm happy with how the race went. There were no errors, I gave everything. I just hope it is enough to get into the final.

"The tight finish shows that it is wide open this year. Although no-one has dominated, a lot of us are all close together. I gave it a good shot, so fingers crossed now."  

On Ashley Spencer's stumble: "I was aware something happened behind but I just tried to focus on my own race and get to that line as soon as possible."

Image source, Reuters

Colin Jackson
Two-time world 110m hurdles champion on BBC One

Ashley Spencer coming back to win is a massive shock. When someone makes a mistake like that you rarely see them come back because there is so much fatigue in your legs. But she managed it.

So close to an automatic place in the final for Eilidh Doyle. She was looking good and at the front of the pack until the final 20m or so, when Ashley Spencer and Janieve Russell powered through.

Doyle crosses the line third and has to wait to find out if her time of 54.99 is good enough to get her through to the final.

Back over in the high jump final, Robbie Grabarz is back on form, flying over the bar to clear 2.29m with ease.

Bran Starc, I am sad to say, is out having failed to clear 2.25m.

Image source, Reuters

Colin Jackson
Two-time world 110m hurdles champion on BBC One

Hejnova, a world champion, knows what it takes to climb that rostrum. The final is going to be good, exciting and I think she might even go quite quick.

Eilidh Doyle is up in the second of three semi-finals. In the first, two-time world champion Zuzana Hejnova powers through to the final with a dominant performance, coming out on top with a time of 54.55. Ristananna Tracey of Jamaica joins Hejnova in qualifying automatically for the final.

Events on the track are coming thick and fast, with the women's 400m hurdles semi-final up now. Great Britain's Eilidh Doyle is among those looking to secure her place in the final.