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.

Flashback: Queen of England meets Trudeau for the 1st time since falling ill

The Associated Press contributed to this article.