The 23-year-old Kenyan, who won the world title over the distance in 2016, knocked three seconds from the previous record set by her compatriot Florence Kiplagat in Barcelona two years ago.
Jepchirchir was part of a seven-woman group during the early stages, passing the five-kilometre mark in 15:40. By 10km, reached in 31:07, Jepchirchir and three-time RAK champion Mary Keitany had opened up a gap of 10 seconds on their pursuers as Olympic marathon champion Jemima Sumgong, multiple world and Olympic champion Tirunesh Dibaba and world marathon silver medallist Helah Kiprop ran as a trio.
Keitany led for a brief moment and was two seconds clear of Jepchirchir as they went through the 15-kilometre checkpoint in 46:30. They were still slightly behind world record schedule, but Jepchirchir had enough in the tank to push the pace for the final quarter of the race.
Jepchirchir, who suffered from pneumonia for two months at the end of 2016, forged ahead and covered the five-kilometre segment between 15km and 20km in 15:09, the fastest split of the race. Having covered the second 10km segment in 30:34, it meant that she reached 20km in a world record* of 1:01:40, putting her on pace to take down the world record for the 13.1-mile distance.
Keitany managed to make up some of the ground in the final kilometre, but Jepchirchir went on to win by a comfortable margin, clocking 1:05:06.
Behind her, Keitany smashed her own best, and nearly the old world record, with a 1:05:13 clocking, while Joyciline Jepkosgei ensured a Kenyan sweep, crossing the newly positioned finish line in 1:06:08, a personal best by almost three minutes. Keitany and Jepkosgei recorded the fastest ever times for second and third place.
In fourth and fifth, Sumgong and Dibaba recorded PBs of 1:06:43 and 1:06:50 respectively. It was just the second time in history that five women have finished a half marathon within 67 minutes.
Karoki comes close to race record
In the men’s contest, world half marathon and cross-country silver medallist Bedan Karoki, so often the bridesmaid on track and cross-country, surged to victory over the last three kilometres in a time of 59:10.
After a group of about 12 men covered the first five kilometres in 14:02, the field was whittled down to just five athletes during the second quarter of the race as they passed 10km in 27:52.
Karoki, Yigrem Demelash, Augustine Choge, Solomon Yego and Kenneth Keter ran together for several kilometres before Keter dropped back, leaving the other four men to reach 15 kilometres in 42:05.
Yego and Choge were the next to fade. Karoki finally managed to drop Demelash just before 20 kilometres, which he reached in 56:10 before going on to cross the finish line in 59:10, a personal best by four seconds and just 18 seconds shy of the race record.
Demelash, last year’s world 10,000m leader, finished second in 59:19, a lifetime best by 29 seconds. Choge, in only his third ever half marathon outing, also broached new ground with 59:26.
Tim Hutchings (organisers) and Jon Mulkeen for the IAAF
1 Bedan Karoki (KEN) 59:10
2 Yigrem Demelash (ETH) 59:19
3 Augustine Choge (KEN) 59:26
4 Solomon Yego (KEN) 59:50
5 Nguse Amlosom (ERI) 1:00:04
6 Edwin Kipyego (KEN) 1:00:05
7 Shadrack Kimining (KEN) 1:00:07
8 Kenneth Keter (KEN) 1:01:05
9 Gabriel Geay (TAN) 1:01:13
10 Adugna Takele (ETH) 1:01:14
1 Peres Jepchirchir (KEN) 1:05:06
2 Mary Keitany (KEN) 1:05:13
3 Joyciline Jepkosgei (KEN) 1:06:08
4 Jemina Sumgong (KEN) 1:06:43
5 Tirunesh Dibaba (ETH) 1:06:50
6 Helah Kiprop (KEN) 1:07:48
7 Rose Chelimo (KEN) 1:08:37
8 Veronicah Nyaruai (KEN) 1:09:33
9 Anne-Mari Hyrylainen (FIN) 1:12:39
10 Etagegn Woldu (ETH) 1:14:46
*Subject to the usual ratification procedures