Assuming the 28-year-old from Whatstandwell in Derbyshire, on board B&Q, her 75ft trimaran, can find a way through to the finish line of the round-the-world course off the Brittany coast before 7.04am on Wednesday, she will be hailed worldwide.

A world record set on a trimaran to go alongside her previous exploits — her twin victories in transtlantic races and her second place in the Vendée Globe single-handed round-the-world race four years ago — would give MacArthur an unmatched career performance, taking her past those who inspired her as a child, the knights of British sailing, Sir Francis Chichester, Sir Robin Knox-Johnston and Sir Chay Blyth.

When MacArthur set off at the end of November, few thought she had more than a 25 per cent chance of breaking the 72-day record set by Francis Joyon, the Frenchman, last year. Joyon had an extraordinary voyage, cutting the previous fastest time by more than 20 days and becoming the first person to get round the world non-stop on a multihull.

When he came ashore this time last year, many thought his record would stand for ten years or more.

Yet in a display of her superlative reserves of courage, stamina and sheer bloody-mindedness in the face of insurmountable odds, MacArthur — small of stature but with the heart of a lion — has forced her boat round the planet, battling against storms, exhaustion and mental stress to keep her record-breaking chances alive during 26,000 miles at sea.

Now, just a little more than 1,000 miles from the finish and with a lead over Joyon’s equivalent position of three days and ten hours, she has her dream in the palms of her battered hands.

The weather, however, remains the one element that she cannot control and, as her shore team in Cowes on the Isle of Wight put it, it is down to what amounts to a “throw of the dice” whether she will make it. MacArthur, who was described as having “hit the wall” with exhaustion as B&Q romped northwards past the Azores, was not taking anything for granted and said that she may reach the finish only a matter of hours either side of the record.

“The problem is that we have to make more gains now, as the weather looks terrible ahead,” she said on her satellite phone in B&Q’s cramped cabin as seas crashed over the boat while it travelled north at about 25mph. “Current routing shows me (finishing) late Tuesday and the trend is getting worse. Now is the only time to make gains. Sail changes are taking twice the time they were earlier in the trip,” she added, underlining that her reserves of energy were close to the limit.

Playing on MacArthur’s mind were her recent and painful memories of light winds in the South Atlantic, where her four-day lead over the record at Cape Horn disappeared by the time she neared the Equator. Her weather advisers in America, who talk to MacArthur up to 20 times a day, are not forecasting that that might happen at this stage and, with luck, she could be through the danger zone by tomorrow evening, leaving the record very much on.

In Cowes, the ten-strong team are seeming to find it harder to bear the tension than their lone skipper, given their increasingly dramatic briefings. “Ellen is 24 miles through a 26-mile marathon, she has hit the ‘wall’, where energy levels drop to irrecoverable levels, she’s torn a few muscles, has bad blisters, and her shoes are close to falling apart,” they reported yesterday.

“She can nearly see the finish, at the top of a very steep hill. She is fighting to win, but she doesn’t know if she can make it.”

MacArthur will come ashore at Falmouth after sailing across the Channel from the Brittany coast, where her finish time will be logged by the World Sailing Speed Record Council, which oversees record attempts.

As MacArthur completes the final miles of her extraordinary voyage, Mike Golding, another British sailor, was last night on course to finish third, on Ecover, in the latest edition of the Vendée Globe race.

With Vincent Riou, of France, the skipper of PRB, expected to win last night, Golding was due to reach the finish at Les Sables d’Olonne, on the French Biscay coast, by tomorrow.