Boyce was a major doubt for these Championships even a week ago due to a stress fracture, and had prepared for Berlin mainly through gym work and swimming.

Despite that, Boyce put in a spectacular effort to remain in the leading group for 35km before the 30 Celsius heat and lack of road miles contributed to him slipping back.

Olympic champion Matej Toth of Slovakia tried to break the field early on by going on a surge after only a handful of kilometres, but was rapidly reeled in by a chasing group of a dozen, containing Boyce.

The Finn Valley walker remained in the top contingent despite their numbers being reduced to eight, including Toth.

But the Slovak drew away again just past the halfway point, going 15 seconds clear of five chasers, again including Boyce, who at 26km nudged up into third place and the bronze medal position.

As Toth broke the race up, Boyce remained a medal prospect until he fell off the main chasing pack with 14km to go, seeing his race position fall rapidly – 5th at 34km, 9th at 40km, 13th at 42km as the continuing kilometres bit at him.

Eventually, Boyce came home 19th in four hours, two minutes, 14 seconds.

At the front, Ukraine’s Maryan Zakalnytskyy caught up and overtook Toth in the final 10 kilometres, and romped to victory in 3:46:32.

Though the Rio champion fell out of the medals for a period, Toth stormed back to take silver 55 seconds behind, with Dzmitry Dziubin of Belarus third in 3:47:59.

Ines Henriquez won the women’s 50m walk as lunchtime temperatures began to drift even higher – it’s due to reach 37 Celsius in Berlin this afternoon, and 38 tomorrow.

“I am fairly knackered. The last 10k was fairly brutal,” Boyce admitted afterwards.

“I knew at the start of the race it was going to be tough. I was prepared, so long as my leg didn’t flare up.

“I was going to finish the race regardless, and I did that.

“I can take some positives out of being out there among the lead group for 30 kilometres and not being intimidated.

“I was in the lead group and felt strong there, reacting to moves.

"Overall I’m happy, but it’s not where I want to be in the end.”

Boyce revealed he was immensely close to not being able to make it to the start line, and it was extra-curricular training that was able to get him reasonably tuned-up for Berlin.

The Finn Valley athlete explained: “I had a stress reaction in my tibia nine weeks ago, so I did most of my training in the gym, cross-training and swimming.

“I have only done about 300 kilometres on my legs since June – we didn’t even know if we were going to race until last week. Even to finish was a positive, and the way I raced was a positive.

“I’ll go home tired but happy.”

At the Olympic Stadium, Claire Mooney of DSD was lying in second place at the bell in her 800m heat, and was still at the head of affairs coming to the final bend, but didn’t have a sufficient kick as the main candidates in the field pulled clear over the final 100 metres.

Mooney was seventh on 2:04.26 as Britain’s Adelle Treacy won in 2:01.91, and told Athletics Ireland post-race: “I think next year I should be stronger. I’m not really sure why I tied up, but I gave it my best.”

After a successful collegiate career at NCAA level in the United States, Siofra Cleirigh-Büttner was sixth in a stellar heat in 2:02.80 as the top three consisted of Ukraine’s Olha Lyakhova (2:00.26), Britain’s Lynsey Sharp (2:00.32) and Selena Büchel of Switzerland (2:00.42) – the latter two of which have been European champions, and Lyakhova won World Student Games silver in Taipei last year.

Cleirigh-Buttner was still reasonably satisfied with how she fared, saying: “I was happy enough with how I fared, with the time and the race and how I ran it.

“I would have obviously liked to have been further up – the main goal is always the top “big Q” but I would have liked to have been in a faster qualifying position.

“I was leaving it a bit thin there with the next few heats, but I was happy enough with how I conducted myself out there. I just wish I had gotten (ahead of) the Italian girl at the end.”

Chris O’Donnell ran a season’s best 46.81 in coming sixth in his 400m heat.

Kevin Borlée won O’Donnell’s heat in 45.29 seconds, and then watched as the other Borlée brothers Jonathan and Dylan took victory in their respective heats also – the first time three brothers have all won races in a single round at a major Championships.

20-year-old O’Donnell expressed satisfaction with his morning: “A season’s best and I’m 20 years of age – I’m the third-youngest competitor here in the 400, so the experience from competing here, I’m going to come on leaps and bounds coming into the years to come.

“I’ll definitely look back on this day as the start as what made me as a senior athlete. I don’t think there’s any junior that goes straight into finals, straight into winning medals.

“You have to have days like this. I’m happy with how I ran and I thought I competed. I was still making ground.”

Tonight, there’s semi-final action for Thomas Barr in the men’s 400m hurdles (6:59pm) and Phil Healy in the women’s 100m (6:05pm), while Stephen Scullion is in a massive field of 32 in the men’s 10,000m final at 7:20pm.