So she's done it. Brave, brilliant, resourceful, resilient Ellen. Sailing's very own Truman Show has come to the happiest of endings.
A fan watches Ellen's latest visit to the B&Q diary room
Around the world, with only a webcam for company, a day and a half faster than previous record-holder Francis Joyon and a whole week better than Phileas Fogg's effort.
The best part of 72 days and over 27,000 miles of sheer... well, what, exactly?
Because that's the problem for those of us who have never sailed a boat around the world.
We know what MacArthur has done is very, very impressive - we're just not quite sure why.
We know sleep deprivation is nasty, we can imagine that fixing your mast in a Southern Ocean storm is fairly difficult and we can also appreciate that nearly colliding with a whale could be quite scary.
But that's about it. From a purely sporting point of view, MacArthur's feat is difficult to assess.
She has not won a race or smashed an iconic barrier - the sub-72-day round-the-world trip has not gripped a generation the way the four-minute mile did.
Neither is MacArthur's accomplishment a "first" of any kind.
Hers is not a Sir Edmund Hillary conquering Everest moment, or, to limit things to sailing, something as history-making as Robin Knox-Johnston's first ever non-stop circumnavigation in 1969.
She is not even the first woman to make the solo trip non-stop. Kay Cottee claimed that honour in 1988.
Sailing's answer to Alan Shearer enters the finishing straight
So, to recap, she is not a winner and she is not the first.
She IS the fastest, but it is not a record we have spent much time worrying about. And she does not "play" a sport that most of us can relate to in a way that we can when rating, say, Dame Kelly Holmes' accomplishments in Athens last year.
So why the fuss?
The answer to that probably has more to do with who she is than what she has done.
Round-the-world sailors are supposed to be tough, tousled and male. They usually have salt water coursing through their veins and their beards, and look as though they knew how to tie reef knots before they could speak.
MacArthur is 5ft 2in, has a tidy crop and is female. She was born, 28 years ago, in land-locked Derbyshire. Hardly the start in life that ensures sailing superstardom.
And that is why we love Ellen. She is perhaps this country's greatest ever sailor - move aside Lord Nelson, Sir Francis Drake, Sir Walter Raleigh et al - and she has done it on her own and against the odds.
The girl that saved her dinner money to buy her first boat is now the holder of off-shore sailing's blue riband record.
MacArthur shares Redgrave's drive and determination
So roll out the superlatives, but go easy on the in-depth analysis of just how difficult it is to take a multi-hull boat around Cape Horn.
The closest comparable achievement is Sir Steven Redgrave's haul of five Olympic rowing golds - another tale of bloody-minded determination and self-sacrifice in a pursuit few of us know much about.
Like MacArthur and sailing, Redgrave was not "born" to be a rower. He made himself his chosen sport's greatest ever exponent by marrying ability to an unparalleled will to win.
"I've met Ellen a couple of times and she is certainly a very quiet and driven person," Redgrave told BBC Sport.
"I was a bit like that when I was competing but I can't imagine doing what she has just achieved.
"She was in a stressful situation where sometimes she only had an hour's sleep. And to only have an hour's sleep and then to be able to keep you mental awareness is something I can't relate to, because I wouldn't have been able to do it."
But the indomitable spirit that sparked Redgrave to Olympic glory also fires MacArthur. And it should earn her a place alongside Redgrave in British sport's pantheon of heroes.
The only question now is will the current Queen Elizabeth copy her namesake and knight MacArthur on board her boat, or will Dame Ellen have to settle for the palace?