Frenchman Vaillant, playing in the first group out on Thursday morning, reeled off six birdies in his final seven holes to set the target at eight under par.

Swede Åberg bounced back from an opening bogey with nine birdies – including three in a row at the end of his round – to sign for a 64 and join Vaillant at the summit.

With around 90 minutes lost following an afternoon weather delay due to thunder and lightning in the area, Thursday’s later starters will return to the course to complete their first rounds on Friday morning after play was suspended due to darkness at 19.30 local time.

Casey Jarvis was the co-leaders’ nearest challenger on seven under after the South African closed his round with five straight birdies.

Home favourite Matt Fitzpatrick, Scotland’s Richie Ramsay, France’s Antoine Rozner and Swede Joakim Lagergren were another stroke further back.