The Royal Family Is Not Allowed To Travel Together By Plane, Boat, Or Train.
A trip with the Royal Family? That necessitates extensive planning! Members of the Royal family should not travel by plane, boat, or train together. They most likely have a vacation planner on staff!
In the event of an accident, the rule was put in place to protect possible successors to the British monarchy from dying simultaneously. As a result, it’s unlikely that Kate will be able to travel with both her husband and her father-in-law, Prince Charles.