After decades of debate, years of acrimony over the issue in the Conservative Party, months of brutal brinksmanship in Westminster, and hours of debate this week, MPs have just approved the very first step in the process of Britain leaving the European Union.
There are many hurdles ahead, probably thousands of hours of debate here, years of negotiations for Theresa May with our friends and rivals around the EU, as she seeks a deal - and possibly as long as a decade of administrative adjustments, as the country extricates itself from the EU.
On a wet Wednesday, the debate didn't feel epoch-making, but think for a moment about what has just happened.
MPs, most of whom wanted to stay in the EU, have just agreed that we are off.
This time last year few in Westminster really thought that this would happen. The then prime minister's concern was persuading the rest of the EU to give him a better deal for the UK.
His close colleagues believed the chances of them losing, let alone the government dissolving over the referendum, were slim, if not quite zero.
Then tonight, his former colleagues are rubber stamping the decision of a narrow majority of the public, that changed everything in politics here for good.
This isn't even the  last vote on this bill. There are several more stages, the Lords are likely to kick up rough at the start.
But after tonight, for better or worse, few will believe that our journey to the exit door can be halted.
As government ministers have said in recent days, the moment for turning back is past.

The fifth most common cancer in UK women affects more than 6,500 a year.
Researchers funded by the Department of Health compared the survival rates of 20,000 patients in five countries - Australia, Canada, Denmark, Norway and the UK. The UK ranked worst.
Its record of managing advanced stages of the disease was particularly poor.
Survival rates have been improving - more than two-thirds of women with this cancer survive more than a year now in England and Wales compared with fewer than half in the mid-70s.
But they still lag behind other countries.
As the symptoms of ovarian cancer are similar to those of other conditions, it can be difficult to recognise until the disease is more advanced, and experts had thought late diagnosis could explain the UK's poorer track record.
But the findings, in the journal Gynecologic Oncology, suggest problems accessing successful treatment are to blame.
Lead author Dr Bernard Rachet, of the Cancer Survival Group at the London School of Hygiene and Tropical Medicine, said: "Our research is the first population-based study to examine whether low ovarian cancer survival in the UK is due to more women being diagnosed with advanced disease, or to the outcome of treatment in the UK being inferior at each stage.
"The results show that the proportion of women with advanced disease is similar to that in other countries, but that survival for women with advanced disease is much lower.
"This suggests that the success of treatment is lower in the UK, and more effort should be made to ensure that UK women with ovarian cancer have the same access to the best treatments."
One year survival was 69% in the UK compared with 72% in Denmark and 74-75% in the other three countries.
Women with advanced stages of the disease fared the worst - 61% survived for at least a year in the UK compared with up to 74% elsewhere.
The UK was also worse at recording how far tumours had spread.
Although these percentage differences may not sound large, they are significant and big in terms of avoidable cancer deaths, say the researchers.
Past work by some of the same team suggested around 500 ovarian cancer deaths a year could be avoided in Britain if the country had a survival record that matched the rest of Europe.
Sara Hiom, of Cancer Research UK (CRUK), said: "This disturbing research advances our knowledge about what needs to be done to tackle lower ovarian cancer survival in the UK."
A recent study by the charity predicted that many cancers would see improvements in survival rates over coming years.
CRUK estimates ovarian cancer death rates will drop by 43% by 2030.
Gilda Witte of the charity Ovarian Cancer Action said: "We believe that women who have reached the advanced stages of the disease should have the opportunity to be treated within expert specialist centres, where they will benefit from the expertise of leading specialist surgeons implementing the latest research within experienced multidisciplinary teams.
"We know that when these conditions are in place, it drastically increases a woman's chance of surviving this terrible disease."
It's begun.
[NEXT_CONCEPT]
Women in the UK are dying unnecessarily of ovarian cancer because of a lack of access to the best treatment, say experts.