Welsh sailor Alex Thomson has halved the gap between himself and Vendee Globe solo race leader Armel le Cleac'h ahead of Thursday's expected finish.
Thomson, 42, trailed by around 70 miles on Tuesday, but cut the deficit to 34 with 309 miles left of the race.
Le Cleac'h was 383 miles from Sable D'Olonne on France's Atlantic coast early on Wednesday.
Bangor-born Thomson and his team claimed a 24-hour world mark of 536.81 miles from Sunday to Monday.
Frenchman Francois Gabart holds the 24-hour record, having set it during the 2012-13 edition.
Gosport-based Thomson is competing in the Vendee Globe for the fourth time, and attempting to become the first Briton to win it.
'It really is all to play for' - MacArthur
Dame Ellen MacArthur finished second in the 2001 race at the age of 24.
She says Thomson can still win, but may have to depend on the Le Cleac'h suffering problems.
"It's not out of the question. I certainly felt with the Vendee Globe, until the person who's racing in front of you has crossed that line, it's all to play for," said MacArthur.
"And what we've seen in the past, there are actually some serious failures just hours from the finish. We've even had keels falling off.
"It would be just as easy for Armel to have problems, which we may not know about so it really is all to play for."
Thomson, the early leader
Thomson led for much of the early stages and broke two race records prior to being overtaken, with Le Cleac'h moving ahead in early December.
Thomson was nearly 1,000 miles behind at Christmas after his boat's hydrofoil was ripped off in mid-November, but has increased his speed since rounding Cape Horn.
|Explained: The Vendee Globe around the world sailing race|
|Thirteen solo sailors took part in the first race in 1989-1990, won by Frenchman Titouan Lamazou|
|The non-stop race is based at Sable D'Olonne, France where it starts and ends|
|It has never been won by a Briton|
|2016-17 is the eighth edition of the race, which now takes place every four years|
|Frenchman Francois Gabart is the race record holder, completing the 2012-13 event in 78 days|