MacArthur, sailing on Kingfisher, has a narrow advantage over her compatriot on board Ecover, in the trans-Atlantic race to the Caribbean island of Guadeloupe.

But she has been having a rocky ride in stormy conditions that have already caused 20 skippers to abandon.

MacArthur's friend and sometime race partner Alain Gaultier has become the latest to retire from the multihull class on Friday.

The Frenchman said his trimaran Foncia had fallen victim to a huge wave during the night.

"It was a pyramid-shaped wave which came in very quickly and took hold of the boat underneath and that's when I heard a big crack."

Swiss sailor Steve Ravussin has now built up a good lead in the multihull class on board TechnoMarine.

And, as the fleet start to round the Azores, Australian Nick Moloney has surged 60 miles clear in the monohull class-two category.

Moloney is a team-mate of MacArthur's at Offshore Challenges.