The European Champs women's 800m semi-finals were run in brutal midday heat on Thursday of 34-35C – probably the hottest conditions at a major UK athletics meet since the AAA Championships in Birmingham back in 1990 – but it was a dramatic late fall for Audrey Werro, rather than the temperature, that ended up as the main talking point.

The Swiss sensation, the fastest woman in the world this year over two laps, was leading her semi-final with around 120m to go when she went down hard. Initially spectators assumed she had been clipped from behind by her own Swiss team-mate but later angles told a different story, appearing to show France's Anaïs Bourgoin catching Werro's foot with her hand as the field jostled for position. Whatever the cause, Werro hit the deck, got back up, and – crucially, as it turned out – finished the race, crossing the line in 2:35.35 to at least give herself a chance of a reprieve.

That reprieve duly arrived. Less than an hour after the race, a small "qR" appeared next to Werro's name in the results, confirming she had been advanced to Friday's final. Lithuania's Gabija Galvydyte, also caught up in the incident and similarly slow in finishing, 2:03.59, was reinstated alongside her. It means Friday's final field has swelled from the usual eight to ten – not without a certain amount of controversy and plenty of drama.

Staying remarkably composed given the circumstances, Werro was simply relieved to have given herself a shot. "I was feeling really great but unfortunately something happened and I was just on the ground," she said. "I hope I will qualify for the final. I finished the race, too, which was important to give myself a chance of qualifying."

Femke Broeders-Bol, who was racing in the other semi-final a few minutes later, admitted she had only seen the incident once rather than picked over the replays. "I saw it but didn't see the replay," she said. "I hope she's okay first of all, but I think that's part of 800m."

Hodgkinson, meanwhile, heard the whole thing unfold as she was getting ready to race rather than seeing it. "I heard a big 'oooh', which is never a good sign, as I was getting ready for my own race," she said. "It's a real shame and I hope she's okay and that she's in the final tomorrow."

As for her own race, she kept it simple: "For me, I just wanted to get through and it was similar to the heats but with a bit more strength in depth. The excitement for this event makes me excited. It brings out the best in me. I hope it's a good race and a clean race. We don't want to see anyone falling over in the final."

Aside from the drama, the first semi-final still had to produce its qualifiers and it did so with Britain's Jemma Reekie sprinting clear of the melee on the final bend to win in 1:58.61 ahead of Bourgoin (1:58.84) and Switzerland's Veronica Vancardo (1:59.14), who took the third automatic spot in the race.

Hodgkinson's own semi-final was the faster of the two by some distance and, unlike Werro's race, played out fairly predictably. She led from the front and controlled it exactly as she wanted, going through 400m in 57.71 on her way to victory in 1:57.38, with Broeders-Bol (1:57.46) and Italy's Eloisa Coiro (1:57.74) following her through automatically.

Switzerland's Valentina Rosamilia and France's Clara Liberman both ran personal bests, 1:58.16 and 1:58.19 respectively, to claim the two fastest-loser spots and give the final its full complement of qualifiers before the two reinstatements were added on top.

With Hodgkinson installed as the favourite for gold and Werro now confirmed for a final she looked to have blown her chances of just an hour earlier, Friday's race has taken on an even sharper edge than the one previewed by the bookmakers earlier in the week – for more on how the betting shapes up between the two of them, see our earlier piece on the odds for an 800m World Record bonus in Birmingham.

It remains to be seen, too, how well Werro recovers in the next 24 hours after falling quite heavily on the Alexander Stadium track.

Women's 800m semi-final 1: 1 Jemma Reekie (GBR) 1:58.61; 2 Anaïs Bourgoin (FRA) 1:58.84; 3 Veronica Vancardo (SUI) 1:59.14; 4 Gabriela Gajanová (SVK) 1:59.32; 5 Rénelle Lamote (FRA) 1:59.88; 6 Marta Mitjans (ESP) 1:59.91; 7 Gabija Galvydyte (LTU) 2:03.59 qR; 8 Audrey Werro (SUI) 2:35.35 qR

Women's 800m semi-final 2: 1 Keely Hodgkinson (GBR) 1:57.38; 2 Femke Broeders-Bol (NED) 1:57.46; 3 Eloisa Coiro (ITA) 1:57.74; 4 Valentina Rosamilia (SUI) 1:58.16; 5 Clara Liberman (FRA) 1:58.19; 6 Smilla Kolbe (GER) 1:58.21; 7 Nina Vukovic (CRO) 1:59.10; 8 Rocio Arroyo (ESP) 1:59.32