Tom Fordyce
Chief sports writer

"Even with all Jessica Ennis-Hill has achieved, to be leading this World Championship heptathlon after four of the seven events is quite remarkable. Less than a month ago she was unsure whether she would compete; just over a year ago she was giving birth to her son Reggie. 

With Katarina Johnson-Thompson in silver and pre-event favourite Brianne Theisen-Eaton down on her form of Gotzis, the day could barely have gone better for British hopes."

PAULA RADCLIFFE
Women's marathon world record holder

"When Mo failed to qualify for the Olympic final in this stadium in 2008, the mistake he made was that he worked way too hard on the training camp where the humidity was higher and he exhausted himself. He's not made that mistake this time. He's ready."

The last time Farah raced in the Bird’s Nest was at the 2008 Olympics where he failed to qualify and suffered what he's described as “the biggest disappointment in my career”. 

“I remember coming back home with my head down, knowing that I could have got to the final but I didn’t,” he has said.. “But I came back four years later in London and that was the most amazing thing ever. Now my aim is to go out there and make history."

Image source, BBC Sport

Daley Thompson
Two-time Olympic decathlon champion on BBC TV

"Mo is up there with some of the greatest long-distance runners of all time, and I expect him to add to his tally of wins here."

Brendan Foster
Olympic medallist and BBC athletics commentator

"I'm sorry to upset the applecart, but Mo has a race on tonight. Geoffrey Kamworor is faster over marathon distance, half-marathon distance and at cross-country level. If he can make it a test of strength, Mo's got a race on his hands. If he leaves it until the last couple of laps, Mo will win. But we could have a classic race here."

Those in the know have been talking confidently about Farah's chances in this final. Neil Black, the performance director of British Athletics, said this week that Farah "owns the start line." 

The Briton on the start line now... bouncing... waiting... the starter gives his orders and away they go, setting off for 25 energy-sapping laps. 

Image source, BBC Sport

Mo Farah sticks his tongue out to the cameraman who is following him as he steps out onto the track. Has there been a more relaxed-looking athlete before a major final? The Briton warming up on the track, sweat running down his face already. A minute or so before the final begins. 

One final track event before the opening day of these World Championships concludes. Mo Farah and the men's 10,000m is our focus. The Briton chasing history - hoping to do another double double. Drum roll, please. 

Denise Lewis
Olympic heptathlon gold medallist on BBC TV

"This was a fantastic piece of running by Katarina. She looked confident in this event."

Jessica Ennis-Hill on top of the leaderboard after day one with 4,005 points, with Katarina Johnson-Thompson second, 80 points behind on 3,925. A British one-two, which is always nice to see. 

Image source, EPA

Season's best times for both Johnson-Thompson (23.09) and Ennis-Hill (23.42) in the 200m. Olympic champion Ennis-Hill leading the standings after day one.  

"The 200m is always a good event for me. With the shot put PB, it's been a good day one," says Johnson-Thompson. 

Ennis-Hill is also smiling, saying: "I am pleased. I have that feeling of slight disappointment because I'm always comparing myself to my best. Generally, I'm really happy to be in this position right now."

Colin Jackson
Two-time world 110m hurdles champion

"That was a good bold performance by Katarina. She got out of the blocks really well, saw the other athletes and picked them off."

A wave and a smile to the camera from Katarina Johnson-Thompson as she's introduced to the crowd for the start of the heptathlon's 200m. 

The Briton in lane four, compatriot Jessica Ennis-Hill outside her in lane six. A hush before the starter presses his gun.  

Johnson-Thompson first coming out of the bend ahead of the rest, she extends her lead and finishes in 23.09 - ahead of Ennis-Hill, who is home in second. 

Image source, Reuters

Jo Pavey
European 10,000m champion on BBC TV

"Mo Farah looks really happy. It must have been tough for him. There were no allegations against him, but it was still tough. But he's come out in great form. Apparently, his training has been going brilliantly in Japan. He's an amazing championship runner. He keeps himself in contention, then takes control when it matters."

Steve Cram
BBC athletics commentator

"Mo's trained very quietly for this. In Japan, you couldn't have seen anybody who was more part of the group. I'm not sure the other athletes can do much to stop him. He has been hurt by what's gone on, and he's retreated into what he knows best. The people around him have done a great job of getting him right mentally. I'm not sure I've ever seen him in better condition for a championship race."

Katarina Johnson-Thompson is measuring the blocks, but let's fast forward to the men's 10,000m final for a moment because double Olympic champion Mo Farah could this afternoon win an unprecedented sixth consecutive world distance title. 

The Briton will attempt to successfully defend his men's 10,000m title at 13:50 BST. The 32-year-old is the favourite, he's in the shape of his life, but his rivals are planning to gang up on him. 

"I think this year my opponents might try something different,” Farah has said. "I think early on they will try to do something to burn me out – or perhaps even tire me out for the 5,000m next week. But we have ticked every box in training.”

Image source, Getty Images

If you're unsure of what event follows what in the heptathlon, hopefully the guide below will help. Next it's the 200m and Jessica Ennis-Hill and Katarina Johnson-Thompson will shortly set off in the fourth heat, bringing an end to the opening day of the heptathlon.

For those of you who love nothing more than casting your votes on the day's burning issues, now is the time for you to come into your own. 

In today's vote, we're asking: how many medals will Britain win at the World Championships? There's a selection for you to choose from on this page, starting at zero and ending with 10+. Remember, it's just for fun.

Image source, BBC Sport

Michael Johnson
BBC Sport athletics expert & 400m world record holder

"Justin Gatlin has come here to run. I think he has a chip on his shoulder about being painted as the villain. He's brought that on himself, but he's come into this with a real chip on his shoulder, and it shows. It's benefiting him in terms of his performance. This aggressive approach that he has taken is working well for him."

Image source, AP