For Queen Elizabeth II, being 89 years old is not a constraint and she does not seem to be slowing down anytime soon. The senior royal, who will celebrate her 90th birthday on April 21, regularly reads an account of the British Parliament’s proceedings written for her by a government whip, while her weekend dispatches include an update on events across the Commonwealth. She receives more than 200 letters daily, of which she reads some and the rest are entrusted to ladies-in-waiting.

She is the oldest and longest-reigning monarch in Britain and the first to enter her tenth decade. She has rights to be consulted by the prime minister, and has powers to appoint bishops and archbishops, according to Matthew Dennison, author of “Queen Victoria: A Life of Contradictions.” Besides, the 89-year-old royal has been given the unique right to ride in a horse-drawn carriage along Rotten Row (a broad track along the south side of Hyde Park in London).

Last year, Elizabeth undertook 341 engagements, 35 of them overseas. Rumors of abdication have been quashed time and again on her behalf by her family, the Royal Household, and constitutional and royal historians. “I don’t think it’s even a thought,” the Duke of York said in 2015.

The queen will ring in her milestone 90th birthday on April 21. However, it will be work as usual for her, as she will undertake two engagements in Windsor with her husband Prince Philip, the Duke of Edinburgh. She will unveil a plaque marking The Queen’s Walkway at the foot of Castle Hill. And later, in the evening, she along with her husband of 68 years, son Prince Charles and his wife Camilla, the Duchess of Cornwall, will attend a beacon lighting ceremony.

Elizabeth will light the principal beacon, and another 1,000 beacons will be lit across the country and worldwide in honor of the queen’s 90th birthday.

Elizabeth and Philip will visit the Royal Mail Windsor Delivery Office on April 20 to mark the 500th Anniversary of the Postal Service. The couple will then visit Alexandra Gardens in Windsor, where they will officially open the new Bandstand and meet children from six local schools. They will also watch a short performance by a children’s choir.

The queen, who is known to believe in low-key celebrations, will usher in her 90th birthday with her family. However, festivities have been lined up at Windsor Castle from May 12-15, featuring 900 horses and 1,500 performers — including dancers, musicians and choirs, along with well-known artists and actors. Besides, her official birthday will be celebrated with fanfare all over the country in June that will culminate with The Patron’s Lunch at the Mall on June 12.

The Press Association has released pictures pertaining to each and every year of her life ahead of her 90th birthday.