The Queen marked becoming the longest reigning monarch in British history with a masterclass in understatement, a simple thank you and the comment: "Inevitably a long life can pass by many milestones."
Reflecting on the landmark record, the Queen admitted it was not a moment she had ever aspired to.
As she opened the £294 million Scottish Borders Railway in Tweedbank on Wednesday, with the Duke of Edinburgh at her side, the Queen said: "Prince Philip and I are very grateful for the warmth of your welcome on this occasion.
"Many, including your First Minister, have also kindly noted another significance attaching to today although it is not one to which I have ever aspired.
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"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."
The 89-year-old monarch has spent the day travelling 40 miles on the railway with Nicola Sturgeon, starting at Edinburgh's Waverley Station, stopping off at Newtongrange in Midlothian before carrying on to Tweedbank.
At around 5.30pm today, the Queen overtakes the record set by her great-great grandmother Queen Victoria to become the nation's longest reigning sovereign, when she will have been on the throne for 23,226 days, 16 hours and approximately 30 minutes.