Princess Charlotte is the Queen’s “favourite” great-grandchild because of her love of horses, a royal expert has claimed.The daughter of Prince William and Kate Middleton, six, is believed to be “pony-mad”, according to editor-in-chief of Majesty magazine Ingrid Seward.The fourth in line to the throne reportedly starting riding at 18 months and follows in the footsteps of Her Majesty, 95, whose passion for horses spans 90 years after she was given her first pony by her grandfather aged four.