The Queen has made a surprise appearance at Paddington Station to see the completed Elizabeth line today.
The 96-year-old monarch joins her youngest son, the Earl of Wessex, for the official visit to the new London Underground line which is named in her honour.
A Buckingham Palace spokesperson told the PA news agency: “In a happy development, Her Majesty The Queen is attending today’s event to mark the completion of the Elizabeth line.
“Her Majesty was aware of the engagement and the organisers were informed of the possibility she may attend.”
The Queen attended the event with the help of a walking cane and wore a Stewart Parvin double-wool crepe coat in bright yellow with a matching dress and hat by Rachel Trevor-Morgan, accessorised with her Singapore brooch.
Her attendance was not publicly announced in advance due to her ongoing mobility problems.
The Queen unveiled a plaque stating that she “officially opened” the Elizabeth line.
Following the Queen's visit, Boris Johnson told the invited guests: “We're all incredibly touched and moved and grateful to her Majesty for coming to open the Elizabeth line today.
“It was fantastic to see her.”
It comes after she made a trip to the Windsor Horse Show on Friday and was the guest of honour at the big “A Gallop Through History” event near Windsor on Sunday.
The latter was the first major event of a slew of festivities planned in celebration of her Platinum Jubilee, to mark 70 years on the throne.
Today’s engagement marks the Queen’s first one outside of the Windsor area since she attended the Duke of Edinburgh’s memorial service in Westminster Abbey in March.
Her Majesty and Prince Edward were welcomed by prime minister Boris Johnson, mayor of London Sadiq Khan, and Transport for London commissioner Andy Byford.
They met staff who have been key to the project and who will run the railway, including train drivers, station staff and apprentices. The line will open to passengers on 24 May.
The Elizabeth line has cost an estimated £18.9 billion and was originally due to be completed in December 2018 on a budget of £14.8 billion. It will stretch from Reading and Heathrow Airport to Shenfield, Essex, and Abbey Wood in south-east London.
Join former BBC Royal Correspondent Jennie Bond to reflect on the Queen’s 70 incredible years on the throne at a Platinum Jubilee panel event run by The Independent on Thursday 17 May at 6.30pm.
The broadcaster and journalist will be joined by The Independent’s Associate Editor Sean O’Grady, Deputy Voices Editor Sunny Hundal and hosted by Deputy Lifestyle Editor Laura Hampson to explore the highs and lows of Her Majesty’s seven decades on the throne.
For more information and to sign up for a ticket visit our Eventbrite page.
Additional reporting by PA