Britain's Queen Elizabeth II reacts during her visit to Paddington Station in London, May 17, 2022, to mark the completion of London's Crossrail project, ahead of the opening of the new Elizabeth Line rail service. | ANDREW MATTHEWS/POOL/AFP/GETTY

Queen Elizabeth II made a surprise visit Tuesday to a train station in central London to see a newly completed subway line named in her honor. The 96-year-old monarch, who has reduced most of her public engagements, appeared Tuesday at Paddington Station to see the east-west Elizabeth Line, which is due to open to the public on May 24.

Calling the event "a happy development," Buckingham Palace said "the organizers were informed of the possibility she may attend."

The queen, who wore a sunshine yellow outfit with matching hat, was joined by her youngest son Prince Edward for the official visit. She was seen smiling as she toured the station with a cane in hand.

The monarch made her first public appearance in weeks on Friday when she attended the Royal Windsor Horse Show, watching her beloved equines perform.

Her public appearances are being closely watched as Britain prepares to celebrate the monarch's 70 years on the throne with four days of Platinum Jubilee festivities June 2-5.

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.­­

The queen celebrated her 96th birthday in April, and CBS News senior foreign correspondent Holly Williams says she still appears to be in fine form for a woman of her age. But she has been seen using a walking stick, and she's pulled out of several events, citing the mobility issues.

The last two years haven't been easy for the matriarch of the House of Windsor. She lost her husband Prince Philip about a year ago, and has seen her second son Prince Andrew engulfed in scandal.

Many in the U.K. will have been relieved to see the queen out and about on Tuesday. Celebrations to mark her Platinum Jubilee — serving a record 70 years on the British throne — kick off at the beginning of June. It is to be a four-day celebration and national holiday, including a military parade, street parties and a pop concert at Buckingham Palace.