The young princess and her mother recently visited sick teenagers

The teenager, who is fifth in line to the throne, was expected to mark the day privately with a meal with friends.

She officially celebrated her birthday several weeks ago with a masked ball, held at Windsor Castle, which had a Victorian-era theme.

The princess said that she found it "exciting" to be in the public eye because her public profile enabled her to help more people.

Before her birthday, the Duchess of York took her daughter to visit a London hospital's teenage cancer unit.

The unit is funded by a charity which has the duchess as its patron.

The visit, held last month at the Teenage Cancer Trust ward at University College Hospital, saw Beatrice spend about an hour chatting with the teenage patients and meeting staff.

The princess said: "Being the person I am, I get to experience life and I can share it with so many people and help so many people.