Either Louise is cut-off somewhere or the OP can't count as there are only six grandchildren - Peter, Zara, William, Harry, Beatrice and Eugenie with Philip and The Queen.
I can't be sure but I suspect it was taken in 2002 for the Golden Jubilee looking at the ages of Harry and Beatrice in particular.
A photo from 1922 of Prince Philip at the age of one on the balcony of the Mon Repo Palace
http://www.corfuland.gr/images/stories/politismos/2021/June/prigkipasfilippos.jpg