Justin Gatlin looked off the pace in the 100m semi-final.

Or was he just playing possum?

Have a look...

Jessica Ennis-Hill
London 2012 Olympic heptathlon champion on BBC TV

"Reece Prescod is at the start of his career and has all that excitement. He is very relaxed, on this amazing stage. It gives you goosebumps to see him run like he did."

Denise Lewis adds: "He is thirsty to learn and is at home in this environment. He just has to enjoy it and I am sure he will."

Image source, Getty Images

Katarina Johnson-Thompson has ground to make up in the women's heptathlon.

She is currently 13th in the standings, 342 points short of Belgian leader Nafi Thiam.

Fortunately the 200m is the final event of the multi-eventer's first day.

At 22.79, her personal best is almost half a second better than anyone else's in the competition.

She will go in the fouth and final race after the weaker runners have had their shot.

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

Usain Bolt had no problems with the blocks this time, he got a better start, and was more patient. He started to slow down at the end. He decided to leave something for later and there looks like there's more to come in the final. He has the confidence to know he can do it when it really counts.

We have around 50 minutes until Usain Bolt gets it on in what will be his final individual race.

Here's how they'll line up...

Image source, .

Almaz Ayana's 10000m is worth a second watch. You don't need to be a connoisseur to get it. Total ridiculous dominance.

Paula Radcliffe
Women's marathon world record holder on BBC TV

That was utter dominance from Ayana. She finished with a fast time but the first 5k was pretty pedestrian. To finish that quickly - no wonder she destroyed the field.

It is scary she can come out and run that fast off no racing and doubts about her fitness. She is definitely in shape. What she can do over the marathon remains to be seen but on that evidence she can run it very fast.

T minus 54 minutes until the 100m final.

Image source, Getty Images

Fan of the discus? Of course you are.

Here's how big Andrius Gudzius of Lithuania won gold.

Little Frank: Wow, Ayana has absolutely burned that field, but was still a full minute (one lap) outside the 10K World Record...

David Langley: Her first race of the season and she wins by that much, and hardly looked out of breath...

DJMonster: That was incredible

Allison Curbishley
BBC athletics expert on Radio 5 live

All credit to Ayana, no one new what form she was in. She hasn't been seen for 11 months, the question was would she be here? To step on a track and deliver a performance like that is so, so impressive.

Image source, Reuters

Agnes Tirop takes bronze for Kenya,

Absolutely astonishing.

Almaz Ayana has carved apart a world-class field, winning in 30:16.33.

And Tirunesh Dibaba makes it an Ethiopian one-two but is almost a minute behind.

Lorraine Moulton: This is INSANE ! The way Ayana is just lapping the world's best 10,000m runners like they're out for a stroll round the park.

Brendan Foster
Olympic medallist and BBC commentator on BBC One

We are witnessing tonight one of the greatest distance runs in history.

Andrew Storey: Absolutely incredible pace from Ayana! Super-human endurance!

Image source, Getty Images

Andrius Gudzius of Lithuania has won gold in the men's discus thanks to a best effort of 69.21m.

Sweden's Daniel Stahl claimed silver with 69.19m, with American Mason Finley taking bronze (68.03).

Steve Cram
BBC athletics commentator on BBC TV

This must be soul-destroying for the other athletes.

Almaz Ayana still looks like he is wearing roller skates while the others are trudging in cement-lined wellies.

She has slowed slightly, the world record might not be on after all, but she is out on her own.