Tom Fordyce
Chief sports writer in Rio

David Rudisha produced arguably the greatest single performance at the London Olympics. He ran that night like some relentless robot - what can he do here tonight?

David Rudisha has run six of the eight fastest 800m races in history.

No pressure Dave, but after a substandard evening on the track I could really do with a fast one...

David Rudisha was the only athlete to break a world record in London, but he looks a long way away from that shape this summer.

Rudisha won the 800m in London in a time of 1:40.91 - a phenomenal time. His best time this year is 1:43.35.

Eilidh Doyle won her heat with reasonable ease, and tells BBC Sport that she's relieved after struggling with the heat. This on the night that there's been delays for torrential rain...

"It wasn’t a great race, but it’s very difficult in the heat you want to conserve as much energy as possible," she said.

"I’m happy that I’ve got the win and I’m through to the next round. I always get quite nervous in the heats, you just want to get out there and go. 

"I never think about medals, I just want to go out there and give a really good performance. I just want to make sure I come off the track knowing that I gave it everything."

Thing about the Olympics is, it is passing in a blur...

Image source, Reuters

In the new revised schedule, I think we have about 10 minutes until the men's 800m final.

The race in London was an absolute classic. Can we get anywhere near it?

Tom Fordyce
Chief sports writer in Rio

Eilidh Doyle comfortable in qualifying - a few little technical things to work on, but she has time. A medal contender in the final if she gets it right.

Flying! An excellent race from Eilidh Doyle, utterly comfortable as she bosses her race from the off to win in 55.46.

Not the fastest, but super smooth. Never in trouble. 

Here is Eilidh Doyle. DEFINITELY. I CAN SEE HER. 

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

When you look at somebody who has gone under 53 seconds you really want to scrutinise how they’ve done that.

Delilah Muhammad is a very rangy runner and she’s very confident in this event.

Xue Changrui of China resembles more a synchro diver rather than a pole vault finalist.

This is brilliant...

Swift! That looked very comfortable indeed for Delilah Muhammad as she cruises through.

Eilidh Doyle WAS NOT in that heat. She's in the next one. I couldn't read my own writing. It's late at night...

Dalilah Muhammad goes in this heat too. She's the only woman to run under 53 seconds this year. 

This is what caused all the problems - the rain....

Michael Johnson
Four-time Olympic gold medallist athlete on BBC One

There will be another race in the 110m hurdles for those that did not qualify from first two races and they can claim a fastest loser spot.

Those athletes that did well in the first race will say 'wait a minute, they have another opportunity, but I don't have another opportunity'. The second race is always faster. Hopefully it gets the competition committee for the IAAF saying 'this is what we do when it rains'.

Eilidh Doyle goes for GB in this next heat. Can she make it through?

She has ran the sixth-fastest time of the year so far. 

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

Ashley Spencer you can tell is a lady that has a lot of speed.

She’s very low over the hurdles – when she approaches the hurdle I half close my eyes because if she hits one she’s going flat on the track.

Ashley Spencer of the US canters to the third heat. She is through. 

You will remember, if you were with us earlier on, that the first two heats of the men's 110m hurdles were run in awful conditions.

Well, after some debate, it appears that those two races will be redone later on tonight - only for those who have not already qualified.

Right?

Right.