The prince had PolG disease, a genetic mitochondrial disorder that prevents the body's cells from producing adequate energy.

Prince Frederik of Luxembourg, the youngest son of Prince Robert of Luxembourg and Princess Julie of Nassau, has died after a lifelong battle with a rare genetic disorder known as POLG mitochondrial disease.

Frederik de Nassau died on March 1, in Paris, a day after internationally recognized Rare Disease Day, which takes place on the last day of February.

Prince William will travel to Estonia next week to visit British troops involved in NATO operations there as part of the UK's drive to show solidarity with its allies and highlight its commitment to the defence of the alliance's eastern flank.

The Prince of Wales will make his first visit to Estonia at the end of next week to meet British troops providing a deterrent to Russian aggression in the region. Prince William will travel in his role as Colonel-in-Chief of the Mercian Regiment to learn more about how British troops are bolstering Nato's eastern flank, the palace said.

The Prince of Wales will visit Estonia on Nato’s front line with Russia to meet British troops providing a deterrent to aggression in the region. William will tour the Baltic state next Thursday and Friday mainly in his role as Colonel-in-Chief of the Mercian Regiment,