Runners around the world were left gobsmacked after watching Sabastian Sawe smash the two–hour barrier at the London Marathon yesterday. 

The Kenyan athlete raced around the 26.2–mile course in just 1hr 59 minutes, 30 seconds – more than one minute faster than the previous record.

So, what was the key to Sawe's success? His shoes.

During the race, Sawe wore adidas' new 'super shoe' – the ADIZERO Adios Pro Evo 3, which is one of the lightest racing shoes ever created.

Weighing just 99g, this is adidas' first sub–100g running shoe which, despite costing £450, is designed to be worn just once. 

The futuristic footwear's hidden trick is a stiff carbon-based structure that helps runners move faster by adding a 'spring-like' bounce to each stride. 

'The adidas family is incredibly proud of Sabastian and Tigist's historic achievements, marking the fastest times humans have ever run in a marathon, said Patrick Nava, General Manager at adidas Running.

'This is a testament to the years of hard work and dedication they have made, alongside our innovation team, who have built a supershoe which breaks new ground in the Adizero Adios Pro Evo 3.' 

The original supershoe, the Nike Alphafly, was initially banned after it helped Kenya’s Eliud Kipchoge run the first sub-two-hour marathon outside of race conditions.

However, new rules from World Athletics have allowed supershoes to return to competitions - provided they have no more than one carbon-fibre plate, with midsole height not exceeding 40mm.

The Adizero Adios Pro Evo 3 was unveiled on 23 April, just days before the London Marathon, and is the cultimation of three years of research. 

While its predecessor, the Evo 2, weighed in at 138g, adidas was able to shave an impressive 39g off the new super shoe.  

'Our goal was two digits on the scale, with better performance than we've ever had,' explained Stephan Scholten, VP Product at adidas. 

To cut the weight, adidas came up with its lightest foam to date, which it calls Lightstrike Pro Evo foam. 

The foam maximises cushioning, propulsion and energy return, while a carbon–integrated system ensures the shoe remains stiff for stability.

'This unique interplay of foam and carbon redefines energy return, propulsion and efficiency in a supershoe,' adidas said.

To cut the weight even further, the company has stripped back almost every component on the surface of the shoe.

It explained: 'Even the smallest components – from laces to stitching – have been obsessively refined to deliver marginal gains that make the difference on race day.'

Finally, the base of the shoe – called the outsole – features strategically placed rubber in the forefoot to provide reliable traction at high speeds, without adding too much weight.

'Creating the Adizero Adios Pro Evo 3 pushed us to think differently from the very start,' Mr Nava said.

'We weren't just trying to improve on what we'd done before, we wanted to see how far we could go. 

'We went through more than a dozen iterations, working closely with our athletes and testing everywhere from our labs in Herzogenaurach to high–altitude camps in Kenya and Ethiopia. 

'At that level, every detail really matters – we were measuring things down to the nearest nanogram. 

'It was a long process, but it's led to something we believe genuinely changes what a race–day shoe can feel like.' 

After breaking the two–hour barrier, Sawe credited 'the role of innovation', likely in part in reference to the super shoe.

He said: 'To break the world record is something I have dreamed about for a long time, and to achieve it means so much to me and to the sport of running.

'It reflects the hard work behind the scenes, the support of my team, and the role of innovation in helping me push beyond limits. I'm honoured to be part of a new chapter for the sport.'

Despite coming in at 39mm in thickness (just below the 40mm limit set by World Athletics for road races), the success of the new shoe is likely to reignite the debate among the running community of 'technological doping.'

This debate first reared its head in 2016 with the launch of Nike's £240 Vaporfly shoes. 

During the 2016 Olympic marathon in Rio, all three male medallists wore a prototype of the trainer, with the same technology extended to track races from 2018.

Experts predict the shoe improved the running economy of highly trained runners by four per cent compared to a normal shoe, and improved performance by three per cent. 

'The same shoe gives you a massive variability among different athletes — even greater than 10 per cent in some cases,' says Professor Yannis Pitsiladis, of the International Olympic Committee.

'How you respond to the shoe can determine if you're going to be an Olympian or watch it on TV.

'You know who is going to win and who can qualify [for the Games].

'Athletes have qualified because they had access to a super shoe. And many who were not running in these shoes didn't qualify.'