Lee Fergusson: Massive pressure now on Greg Rutherford. Come on Greg! You can do it! 

If you missed it, here's what happened when GB's Matthew Hudson-Smith finished third to put him through to the semi-finals in his first Olympics.

Katharine Merry, a bronze medallist for Great Britain at the women's 400m in the 2000 Olympics, has been watching the men's 400m heats with interest.

Martyn Rooney failed to advance out of the heats, but Matthew Hudson-Smith moved into the semi-finals.

The next final sees Michael Phelps back in the pool. Joseph Schooling of Singapore is the surprise medal contender though.

Singapore have never won a gold medal. 

Heptathlon leader Nafissatou Thiam puts in a decent shift around the 200m, coming third in her heat in 25.10 seconds for 878 points towards her tally.

That's a little outside her personal best.

A spanner in the works, and joy unconfined for Maya Dirado. Hilary Caldwell of Canada took bronze. 

The British duo of Katarina Johnson-Thompson and Jessica Ennis-Hill are not up until heat four - but event leader Nafissatou Thiam is in action in heat one.

It's not the Belgian's strongest discipline. Let's see how she goes...

Katinka Hosszu right on world record pace at the final turn...

Katinka Hosszu out like a scalded cat, she's three tenths up after the first 50m. Not sure anyone will catch her from here...

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

Martyn Rooney, who helped Great Britain to a bronze medal in the 4x400m relay at the 2015 World Championships, has failed to make it into the semi-finals of the men's 400m after only finishing fifth in his heat.

He should be disappointed. It was not the type of performance he knew he would have to put in. We have seen this from him before.

Image source, AP

The swimmers are in place for our first final of the night. A fourth gold for Katinka Hosszu? Can anyone stop her?

Britain's defending champion Greg Rutherford is up again after fouling on his first jump.

It's long. It's... a foul again.

Rutherford looks behind him to see a red flag raised and shakes his head in frustration.

One more no-jump and Rutherford's Olympics are over before they barely started.

Great Britain's Matthew Hudson-Smith has moved into the men's 400m semi-finals in his first Olympics. The 21-year-old spoke to BBC Sport after finishing third in his heat.

"It was difficult in lane two," he said. "Everyone told me to treat it like a final. I thought I had second, but made a rookie mistake. But I negotiated the round and got through, that's all I could do.

"It is very surreal and I'm just soaking it up round by round. The semi-final is going to be very tough and you have to take every round like a final. The first part is done and it is on to the next round. It is about who wants it more."

Darren Campbell
Former British sprinter on BBC Radio 5 live

Her team feel like KJT’s going to fly in the 800m. What I love about our heptathletes is they’re not quitters.

We might be up here all doom and gloom but we’ve never seen an athlete get seven world-class personal bests in one heptathlon.

Martyn Rooney is OUT of the 400m. A frustrating and disappointing run has cost him. His race is over. 

Michael Phelps has four golds in the pool in Rio so far - and tonight Katinka Hosszu of Hungary will aim to join him.

The 'Iron Lady' has already won the 100m backstroke, the 200m individual medley and the 400m individual medley.

Tonight she goes in the 200m backstroke (02:03 BST).

No relays in her list of wins. Does that make it even more impressive?

Image source, Getty Images

Hopefully enough for GB's Martyn Rooney.

According to himself, to paraphrase, not his best race. But, a fifth-placed finish leaves him in a chance for qualification for the semis tomorrow.

He is in the last place with one heat to go. 

American Lashawn Merritt won Olympic gold in the 400m at the 2008 Olympics and eased into the semi-finals in Rio by winning his heat.

"I felt good," he told BBC Sport. "I wasn't able to compete in 2012 but I'm here to win it. I will take the 400 a round at a time and focus on each race."

Image source, Getty Images