The Queen has made a surprise visit to Paddington Station to see the completed Elizabeth line.
The longest reigning head of state is just over two weeks away from her Platinum Jubilee celebratory weekend to celebrate 70 years as monarch.
A Buckingham Palace spokeswoman said: "In a happy development, Her Majesty The Queen is attending today's event to mark the completion of the Elizabeth line.
The Queen rallied to make a trip to the Windsor Horse Show on Friday and on Sunday was the guest of honour at the equestrian extravaganza A Gallop Through History near Windsor, the first major event of the Jubilee festivities.
The Queen and Prince Edward were welcomed by Prime Minister Boris Johnson, Mayor of London Sadiq Khan and TfL commissioner Andy Byford.
The Queen was also given an Oyster card and shown how to use it on a ticket machine.
Unveiling a plaque stating she had "officially opened" the Elizabeth line, named in her honour, the monarch spent 10 minutes in the station before departing, escorted by Prince Edward.
Afterwards, Mr Johnson said: "We're all incredibly touched and moved and grateful to Her Majesty for coming to open the Elizabeth line today.
The earl then returned to the concourse ahead of a return journey on the railway from Paddington to Tottenham Court Road.
Even though it's not every day that you have a rail line named after you, there hadn't really been much expectation the Queen would attend today's Elizabeth line official opening.
If the new line will help the public get around, the Queen, stick in hand, seems to be tackling her own mobility problems.
TfL says the Elizabeth line will boost capacity and cut journey times for travel across the capital.
It will stretch from Reading, in Berkshire, and Heathrow Airport, in west London, to Shenfield, in Essex, and Abbey Wood, in south-east London.
The new line is expected to slash journey times from Abbey Wood in south-east London to Paddington by almost half, to 29 minutes.
However, passengers wishing to travel the length of the line will still need to change at Paddington or Liverpool Street stations, depending on their destination, until next year?