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The women's 1500m field is more stacked than a hammer-throwing Russian.

In the first heat, we have defending world champion Genzebe Dibaba of Ethiopia and Olympic 800m champion Caster Semenya alongside Britain's Jessica Judd.

The second features Scotland's Laura Muir up against the Netherlands' Sifan Hassan who has the three fastest times of the year.

And the third and final includes Olympic champion Faith Kipyegon and Britain's Rio finallist Laura Weightman.

Two-time Olympian Wallace Spearmon Jr has his say on the 100m and he thinks we will see a battle rather than anyone breaking clear...

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Around one hour until Usain Bolt time. He's currently out on the practice track but looks as though he doesn't have a care in the world...

Michael Johnson, four-time Olympic gold medallist athlete on BBC TV, says: "He knows that if he is stressed before a race he can't perform. He has got his routine before a race and he will probably catch the attention of one of those young kids who will think 'oh he looks relaxed, I think I'll try that too'. Big mistake!

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Greg Rutherford's hopes of recreating his London 2012 heroics ended with a crocked ankle.

Instead all eyes will be on South Africa's Luvo Manyonga. The 26-year-old South African finished fifth in Daegu 2011, but returned home and lost his form and fortune as he developed a crystal meth addiction., external

But he fought back, won silver at Rio 2016 and has the four longest jumps of the year so far.

Is this week the culminating chapter of the ultimate redemption tale?

The United States' Jeff Henderson is the man who beat Manyonga in Rio and is in place here.

They will be hoping to land a leap of 8.05m or a top-12 finish to get into Saturday's final.

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The big discus lads get the field events under way. No Britons involved, but some interesting early form pointer for reigning world champion Piotr Malachowski and Sweden’s Daniel Stahl, whoproduced the farthest discus throw in the world for four years in June.

A throw of 64.50 or a top-12 finish gets you a spot in the final.

Image source, AFP

The varying standard in the men's 100m preliminaries makes from chunky winning margins.

In the second heat Emre Zafer Barnes, Jamaican-born but now representing Turkey, canters home a good two second clear of Tuvalu's Ielu Tamoa on his inside.

Two seconds looks like a country mile on a home straight 100m.

Darren Campbell
Former British sprinter on BBC Radio 5 live

It's not so much Usain Bolt, it's the fact this stadium is full, taking us back to those emotions and feelings we had in London 2012. As an athlete, this is where the excitement just builds and builds. You work towards that moment where you walk into this stadium and it gets your heart building.

You can see Usain walking around that warm up track with that swagger, showing other sprinters, I am Usain Bolt, I am the greatest and I am ready.

Listen to Darren and the 5 live team. Just click 'BBC Coverage' at the top of this page.

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

Usain Bolt brings something extra to the World Championships. He's a big reason why so many have turned up tonight but so many people want to see the next people coming through too.

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Mike Costello
BBC Radio 5 live athletics commentator

It's impossible not to cast your mind back five years ago to the wonders of London 2012. We have been talking about how the sport needs a lift and it has one on the first night here, a sell out 70,000 crowd.

As we followed the hoards coming in we saw what we thought was a first at an athletics meeting, traders selling Usain Bolt scarves. A festival atmosphere, just what is needed.

Listen to Mike and the 5 live team. Just click 'BBC Coverage' at the top of this page.

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

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This crowd is amazing. It doesn't matter what is going on tonight whether it is the prelims for the 100m or the final. These fans have been waiting for a major event to come back to London and they're going to be rewarded with great athletics over the next 10 days.

19:30 - Men's long jump qualifying

19:35 - Women's 1500m qualifying (Jessica Judd in heat one; Laura Muir in heat two; Laura Weightman and Sarah McDonald in heat three)

19:45 - Women's pole vault qualifying - (Holly Bradshaw in group A)

20:20 - Men's 100m first round - heats and lane draw TBC after the prelims (CJ Ujah, James Dasaolu and Reece Prescod)

20:45 - Men's discus qualifying

21:20 - Men's 10,000m final - (Mo Farah)

Image source, Reuters

Mayor of London Sadiq Khan addresses the crowd: "It has been a painful few months for London. A tragic fire and terrorist attacks in our capital. While our city heals, tonight we show that in spite of everything we remain united. Those who seek to divide us and destroy our way of life will never succeed. It's impossible to suppress the spirit and soul of this amazing city.

"Today, London stands as a beacon of equality and respect. A city admired across the globe for its diversity and openness.

"On this momentous occasion, it fills me with pride to join you all and declare London open. Open to the world's athletes, open to the world's sport fans, open to the IAAF World Championships.

"Welcome to London 2017..."

Tom Fordyce
Chief sports writer at London Stadium

Can you truly love more than one opening ceremony in your life? For many people who watched in this stadium or on television five years ago, the moment when the Queen appeared to free-fall out of a helicopter in the company of James Bond was the point when all future sporting events might as well have started by waving a white flag.

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The first action will feature small fry rather than big guns.

These 100m prelims are for the likes of Tuvalu’s Ielu Tamoa who has a personal best of 12.73 – over three seconds slower than Usain Bolt.

You know that one of Tuvalu's biggest income streams is revenues from the licensing of the .tv web domains it was handed in in the early days of the internet?

Nice work if you can get it.

A reminder that you can now watch live coverage of the men's 100m preliminaries on the BBC Red Button, Connected TVs and online at the top of this page.

Here are the coverage times and channels:

18:55-19:30, Red Button - men's 100m prelims

18:00-22:30, Connected TV and online - uninterrupted coverage

19:00-22:00, BBC One

19:00-22:00, BBC Radio 5 live

22:00-22:30, BBC Two - day one review

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So we all love Usain Bolt right?

But if you could sit (or maybe jog) with the great man for five minutes, we want to know what you would ask him and why? How do you think the conversation would go?

Tweet us on #bbcathletics.

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British Athletics have been set a target of six to eight medals by UK Sport. It seems the BBC Sport team are largely in line, though Michael Johnson is perhaps delivering a dose of transatlantic reality!

In his defence he says: "In international competition we ranked by gold. I am ranked above Colin Jackson at least, giving more golds than Colin."

Steve Cram gives his take: "It's up to the athletes to go out and perform. We've got chances haven't we? Our relay teams have chances, Andrew Pozzi, Holly Bradshaw, Laura Muir. There are lots of athletes in the zone if you like but they won't all deliver, one or two will and we may get a surprise somewhere."

Meanwhile on the track, we have had the Gamesmaker choir hitting the high notes with a version of Elbow's First Steps, Rebecca Ferguson giving the National Anthem a working over and now the speechifying.

First up the Duke of the York, then a bit of Lord Coe.

London Mayor Sadiq Khan is next up in this freestyle battle,

No doubt who these fans have come to see...

Image source, Reuters

We've found him... easier than Michael thought!

Here he is: It's Hero the Hedgehog, the official mascot of London 2017.

Image source, Getty Images