It has been a dramatic opening day in Budapest.

Scroll down to read all of the best reaction and watch the highlights, including Britain's first medal of the championships.

For full details head over here.

On Sunday the heptathlon continues, while the fastest man in the world will also be crowned.

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

We saw the rest of the Great Britain team on the balcony cheering for them. It's day one of the championships and we've come away with a silver medal. It's a great start.

Great Britain's first medal of this championships came in extraordinary fashion in the 4x400m relay.

It looked like a two-way battle for gold between leaders Netherlands and second-placed United States but with yards to go, Dutch runner Femke Bol stumbled as she stretched for the line.

That left GB with an open goal - able to stroll across the line and take silver.

Paula Radcliffe
Former women's marathon world record holder on BBC TV

Where you want the appeals to come in is if it knocked you out of a medal. You can't go and re-run a 10,000m final.

We feel a little bit robbed having watched that 10,000 final and we saw Sifan Hassan come back when it looked like she wasn't going to race.

It adds a little bit of fire to the rest of the week.

In an extraordinary women's 10,000m final, Sifan Hassan looked to have gold in her grasp but stumbled in the final seconds and ended flat on the track.

She said she was pushed but played down the prospects of an appeal.

It was Gudaf Tsegay who Hassan tussled with, the Ethiopian taking the gold.

Denise Lewis
Olympic heptathlon gold medallist on BBC TV

Zharnel Hughes looks pretty relaxed and he's wearing his title as fastest man this year pretty well.

Harry Poole
BBC Sport in Budapest

What an opening night.

I said it should be a memorable championships...

Several thrills and a couple of nasty spills later, that is day one done and dusted - and it leaves GB eyeing medals on Sunday.

There's been a terrific atmosphere on Budapest's curtain-raiser. Bring on the next eight days!

We had the men's 100m heats tonight with all three British men - Zharnel Hughes, Reece Prescod and Eugene Amo-Dadzie all progressing.

Noah Lyles, Fred Kerley and Olympic champion Marcell Jacobs all also went through.

Katarina Johnson Thompson speaking to BBC Sport after winning her 200m heat to sit second in the heptathlon: "It felt better than the time that was shown.

"It has been a gruelling day. All of us have struggled with the [rain] delay.

"We've been up since half six. I think this is a different heptathlon. I'm proud to be keep knocking on the door and I'm happy with the finish."

Yemi Mary John spoke to BBC Sport after winning silver for Great Britain in the 4x400m mixed relay: It was a fight and we knew it would be. My last 100m is my strongest and I had to do what I'm good at and close.

Rio Mitcham said: It means everything. A medal can change your life and that's why I can't stop smiling.

Image source, Getty Images

Laviai Nielsen, one of Britain's silver-medal quartet, says Joe Brier was injured during the first leg of the heat this morning but kept going, running 300m while hampered.

That's why he didn't take part in the final.

Harry Poole
BBC Sport in Budapest

There's a whole lot of love for Stetson-wearing Ryan Crouser here.

The American, who first started wearing the hat to meets as a dare, pulls out his finest headwear after delighting the crowd with that stunning championship record throw for world gold.

And we really must repeat that he is doing this with two blood clots in his lower leg. Some performance.

Image source, Getty Images

Femke Bol speaking to BBC Sport after the 4x400m mixed relay: "To be honest I don't have a clue. I've had it once before. I went to go and I'm really sorry for my team. I should finish it off. I have tired legs, think I've had worse tired legs. It happened and it sucks big time."

Image source, Getty Images

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

You can be the best technical runner, you can be the most experienced athlete. I'm still in shock, my heart is pounding. I can't believe we have just seen that back-to-back.

Image source, Getty Images

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

When the lactic kicks in, all you can do is stay within yourself. The real detrimental thing is what we just saw in those two races. You end up out of the medals completely.

"It happened and it sucks big time," Bol says, speaking to BBC Sport.

Image source, Getty Images

It looked like Femke Bol hit her head as she fell too.

She's supposed to be running the 400m hurdles later in the week.

Denise Lewis
Olympic heptathlon gold medallist on BBC TV

You just couldn't write it could you? The Dutch have come out with a slender team. These are both medal winners in these events. It was almost a carbon copy of each other. It was just incredible.

This was the first of those Dutch tumbles. What drama.

Image source, Getty Images

Lewis Davey, Laviai Nielsen, Rio Mitcham and Yemi Mary John are your silver medallists for Great Britain.

Joe Brier gets one too for his run in the heat this morning.