Queen Elizabeth made a surprise visit to a train station in London to see a newly completed subway line named in her honor.

On Tuesday the 96-year-old, who is celebrating 70 years on the throne, was spotted at Paddington Station, where she unveiled a plaque stating she officially opened the Elizabeth Line. The reigning monarch wore a sunshine yellow outfit with a matching hat adorned with blue flowers. Beaming, she slowly walked with a cane in hand as she met with workers.

The queen, accompanied by her youngest son Prince Edward and Prime Minister Boris Johnson, was given an Oyster card and shown how to use it on a ticket machine.

Queen Elizabeth

Queen Elizabeth II attends the Elizabeth line's official opening at Paddington Station on May 17, 2022, in London, England. (Andrew Matthews - WPA Pool/Getty Images)

"We’re all incredibly touched and moved and grateful to her Majesty for coming to open the Elizabeth Line today," said Johnson, 57. "It was fantastic to see her."

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Buckingham Palace called the visit "a happy development," noting that "the organizers were informed of the possibility she may attend."

The new east-west train line will open to the public on May 24.

Queen Elizabeth surprise visit.

Queen Elizabeth II using an Oyster card machine as she attends the Elizabeth line's official opening at Paddington Station on May 17, 2022, in London, England. (Andrew Matthews - WPA Pool/Getty Images)

The appearance marks the queen’s first one outside the Windsor area since she attended a memorial service for her late husband Prince Philip at central London’s Westminster Abbey seven weeks ago.

But the queen has been on a roll during the Platinum Jubilee season. On Friday, Elizabeth made her first public appearance in weeks when she attended the Royal Windsor Horse Show, where she watched her beloved equines perform. Then on Sunday, she was the guest of honor at an equestrian show near Windsor, where Hollywood stars like Tom Cruise and Helen Mirren were guests.

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Elizabeth’s public appearances are being closely watched as Britain prepares to celebrate her 70 years on the throne with four days of Platinum Jubilee celebrations from June 2 to 5.

Prince Edward

Prince Edward rides on an Elizabeth Line train to mark the completion of London's Crossrail project at Paddington Station on May 17, 2022. (Andrew Matthews - WPA Pool/Getty Images)

Last week, she asked her son and heir to the throne Prince Charles to preside over the state opening of Parliament and deliver the Queen’s Speech, which lays out the government’s legislative program.

Palace officials have said she is experiencing "episodic mobility problems" in recent months and has difficulties moving around.

Her grandson Prince William, who is second in line to the throne, has also stepped up in a major way.

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Prince William

Prince William conveyed his condolences to UAE's new President Mohammed bin Zayed Al Nahyan over the death of President Sheikh Khalifa bin Zayed Al Nahyan, in Abu Dhabi, UAE on May 16, 2022. (Ministry of Presidential Affairs/Handout/Anadolu Agency via Getty Images)

For the first time, Elizabeth asked the Duke of Cambridge, 39, to represent her following the death of a foreign ruler. William traveled to the United Arab Emirates to pay condolences following the death of His Highness Sheikh Khalifa Bin Zayed Al Nahyan, president of the United Arab Emirates and ruler of Abu Dhabi. He met with Sheikh Mohammed bin Zayed Al Nahyan, who has been appointed president of the United Arab Emirates.

William was likely tapped for the trip due to the queen scaling back on her overseas travel due to her mobility issues. Charles, 73, is scheduled to start his royal tour of Canada on Tuesday.

The Associated Press contributed to this report.