It raced along at record-breaking speeds in 2016 and '17, required some repairs after spluttering in 2018, but appears to be running smoothly again in 2019.
Steered by the brash and inimitable Eddie Jones, it has been quite the ride on England's chariot during this wild Rugby World Cup cycle. All that's ever mattered, though, is that it parked up in Japan in prime shape for England's tilt at winning the Webb Ellis Trophy for a second time.
That appears to be the case.
England's final hit-out of any consequence ahead of the first World Cup on Asian soil resulted in a 57-15 thrashing of Ireland at Twickenham last month. The way England overpowered the Irish in virtually every aspect revived memories of the winning run under Jones of 17 straight matches from February 2016 to March 2017, taking in two Six Nations titles (including one Grand Slam) and a rise to No. 2 in the world ranking behind the All Blacks.
England fans sang their rugby anthem "Swing Low, Sweet Chariot" with gusto. All the talk then was of a two-way duel between England and New Zealand at the World Cup. But it hasn't quite worked out that way.
England's slump was fairly dramatic, a fifth-place finish in the 2018 Six Nations — its worst in 30 years — being followed by a lost test series in South Africa. Selection was muddled, key injuries took hold, and it seemed like a storm was brewing around Jones.
He has dealt with it all, and will lead England into the World Cup in bullish mood, while also keeping his players on their toes.
"Are we moving in the right direction? Yes," Jones said. "Are we ready to win the World Cup now? No."
Yet in the past year, some of his selections have crystallized, some maybe fortuitously, some fitness permitting.
A back row of Billy Vunipola, Sam Underhill and Tom Curry. A midfield three of flyhalf George Ford and centers Owen Farrell and Manu Tuilagi. Joe Cokanasiga is now unlikely to be dislodged as opposite winger to Jonny May. Dylan Hartley's injuries have allowed Jones to ease Jamie George in as hooker without having to drop his captain.
There are two high-class options at fullback in Elliot Daly and Anthony Watson. The options at lock are formidable, with Maro Itoje and George Kruis still ahead of Joe Launchbury and Courtney Lawes.
Then there's the unlikely story of Lewis Ludlam, who wasn't even in Northampton's top team at club level this time last year but was called into England's World Cup squad after just one international appearance. Watching him in that match against Wales last month was Sandra Taylor, Ludlam's former primary school teacher for whom he promised to get tickets if he made his England debut.
In many ways, there is an embarrassment of riches for England, which is to be expected for the world's richest rugby union.
But some issues still remain.
Only six months ago, Jones was doubting his players' mental resilience after they gave up a 31-0 lead against Scotland to draw 38-38 in a Six Nations match, saying he'd hire a psychologist to help tackle their apparent inability to handle pressure. That pressure will only ramp up in a World Cup.
Four years have passed and many players have come and gone, but have England truly gotten over the humiliation of being the first host nation to fail to get out of pool stage at a Rugby World Cup?
Game-changing players like Tuilagi and Vunipola are susceptible to injury, especially when matches come thick and fast as they do in World Cups.
And can anyone really just brush off Wales' domination of the English when it really mattered in the crucial match of this year's Six Nations, a 21-13 win for the Welsh in Cardiff?
Then there's the tough group England finds itself in Japan, alongside France and Argentina. One of rugby's big gun is sure to fall before the knockout stage.
A plus for England is that the team starts the World Cup with matches against the weakest opponents in the pool in the form of Tonga and the United States, giving the players a chance to settle into the competition and Jones the option to rotate some players.
Then comes the moment of truth, when four years of planning are put to the test.
Jones guided Australia to the 2003 World Cup final on home soil, and was hailed as one of the masterminds behind South Africa's Rugby World Cup triumph in 2007, through his short-term role as technical adviser. As Japan coach, he helped deliver the most extraordinary moment of the 2015 Rugby World Cup when his team stunned the Springboks in the most unlikely win in the competition's history.
Has the wily Australian got another trick up his sleeve four years on? Don't bet against it.
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