LONDON — Kensington Palace has released a portrait to mark Prince George's fourth birthday.

The son of Prince William and his wife Kate celebrated his birthday Saturday. George, who is third in line to the throne, is beaming with a happy smile in the photo.

The palace said William and Kate "are delighted to share a new official portrait of Prince George to mark His Royal Highness's fourth birthday." It was taken by a professional photographer. In the past, Kate has released photos she has taken of the children.

George and his 2-year-old sister Princess Charlotte have been traveling with their parents this week on an official visit to Poland and Germany.

In Germany, George toured a helicopter similar to the one his father William has flown as a rescue pilot.