Russian hearts were broken inside the Luzhniki Stadium as the home favourite Mariya Savinova, known as ‘the chess player’, was tactically out-manoeuvred by the unheralded Kenyan Eunice Sum in an absorbing final.

Sum, the nearest pursuer to long-time leader Alysia Johnson Montano, ran a clever race to stave off the challenge from Savinova down the home straight to pull off one of the biggest surprises of the championships. She smashed her personal best – which was 1:59.13 prior to the final – by nearly two seconds to defeat the Russian by 0.42 in a time of 1:57.38.

The fast-finishing Brenda Martinez also set a personal best of 1:57.91 for bronze to earn the USA’s first ever medal in this event at the World Championships. The courageous Montano, who had led for 750m of the race, suffered the despair of fourth. Yet today was all about a Kenyan woman called Sum.

Savinova looked composed at the start when her name was announced to a near-full house crowd, who then chanted her name rhythmically, generating an atmosphere which must have given the Olympic champion goose bumps.

Predictably, Montano – who loves to play the rabbit – burst into the lead and passed 200m in 26.80, already holding a five-metre advantage from Sum.

This pattern of the race continued for the next 200m as Montano further stretched her lead out to eight metres from Sum with a further four-metre gap back to the main bunch led by Czech Lenka Masna and followed by Natalia Lupu of Ukraine with Savinova back in fifth.

Down the back stretch for the second time Montano still held a huge lead but her stride was gradually shortening, while Sum and the rest of the pack – now led by Savinova – were starting to close.

Around the final bend, the US long-time leader still held a three-metre advantage but was finally starting to pay the price for her ferocious first-lap pace. Sum was second on the inside with Savinova half a stride behind the Kenyan on her outside looking ready to pounce in trademark fashion.

Yet as Montano’s challenge finally wilted and Savinova was about to strike, Sum appeared to find a second wind and started to forge ahead. Roared to the rafters by a passionate home crowd, many expected Savinova to rise to the challenge, but instead it was the 25-year-old Kenyan, who prior to Moscow had not competed in an 800m this year outside of her own country, who was pulling ahead.

Entering the final 20m it was clear that Sum, a World Championships semi-finalist at the 2011 edition, would triumph which she did in a personal best.

Savinova, who seemed to be running through treacle in the final few strides, hung on for silver while Martinez, who had been back in seventh at the bell, powered through on the inside to snatch bronze.

An exhausted Montano dived for the line and toppled over an agonising fourth for the second successive World Championships.

The second Russian, Olympic bronze medallist Ekaterina Poistogova, placed fifth in a season’s best of 1:58.05 with teenager Ajee Wilson – and definitely one for the future – setting a US junior record of 1:58.21 in sixth.

Lupu placed seventh with Masna back in eighth.

Steve Landells for the IAAF