That team turned out to be Kenya, whose national record still fell almost 6 seconds behind as a time qualifier.

Out of the blocks Jura Levy opened up a gap on the US to her inside and gained on Trinidad and Tobago's Kamaria Durant to her outside.

Jackson slightly pulled away from the last visible competitor, China's Liang Xiaojing already down a full lap's stagger two lanes away.

Out front, Forbes passed to Elaine Thompson before any other team's anchor runner even had started to move.

Townsend regained her stagger advantage and a little more going into the USA handoff to Shalonda Solomon but Germany's Gina Lückenkemper quickly gained through the turn opening up a 2-metre lead.