Elizabeth, the second of her name, The Queen of The United Kingdom of Great Britain and Northern Ireland and of sixteen Commonwealth nations, as of September 9th at 17:30 BST has reigned for approximately for 23,226 days, 16 hours and 30 minutes, and, therefore, has surpassed the reign of her great-great-grandmother Queen Victoria.
This makes her the longest reigning monarch in British history.
If you expected the usual pomp and celebration in what is, after all, an historical moment in the royal family, think again; the Queen chose to mark this milestone in an understated way.
It was business as usual for the Monarch as she traveled by stream train from Edinburgh to Tweedbank to formally open the Scottish Borders Railway. She was accompanied by her husband, the Duke of Edinburgh Prince Philip, and Scottish First Minister Nicola Sturgeon.
The only indication of the event was when the Queen gave a brief speech:
Inevitably a long life can pass by many milestones - my own is no exception - but I thank you all and the many others at home and overseas for your touching messages of great kindness.
Back in London, though, a flotilla of historic ships, cruisers, and passenger boats sailed along the Thames River. One of these ships, the HMS Belfast, conducted a four gun salute.
In the House of Commons, the session was postponed for half an hour to mark the occasion. Prime Minister Dave Cameron has described her Majesty as a "rock of stability" in an era where so much has changed.