The Queen made an unplanned visit to London’s Paddington station on Tuesday to see the completed Elizabeth Line.
The 96-year-old monarch, who now rarely carries out public engagements outside of her royal residences, joined her youngest son the Earl of Wessex for the official visit on Tuesday.
She arrived at 11.32am, stepping carefully from the transparent lift while holding a walking stick.
The nation’s longest reigning head of state is just over two weeks away from her Platinum Jubilee celebratory weekend.
The Queen and 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.
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.
“Her Majesty was aware of the engagement and the organisers were informed of the possibility she may attend.”
Crossrail, the project to build the new east-west railway, was delayed and over budget due to numerous issues including construction difficulties and complications installing signalling systems.
It was due to be completed in December 2018 and was set a budget of £14.8 billion in 2010.
The total cost has been estimated at £18.9 billion, including £5.1 billion from the Government.
It will stretch from Reading, in Berkshire, and Heathrow Airport, in west London, to Shenfield, in Essex, and Abbey Wood, in south-east London.
Trains will initially operate in three sections, which are expected to be integrated in the autumn.