Poignant truth behind Prince Louis' name - as Prince William and Kate Middleton pay tribute

Four days after welcoming their third child, and proudly announced the name of their newborn baby boy - Louis Arthur Charles.

Louis was born on Monday April 23 2018 at 11.01am, weighing 8lb 7oz. A short statement from the Palace later confirmed: "The Duke and Duchess of Cambridge are delighted to announce that they have named their son Louis Arthur Charles. The baby will be known as His Royal Highness of Cambridge." Royal fans immediately began to speculate about the meaning behind his first name - and it's believed it was in honour of someone once considered one of the "secret weapons". The family member in question is , a grandson of - who was born Prince of Battenberg.

Lord Mountbatten was born in Windsor at House and christened Louis Francis Albert Victor Nicholas by his parents Princess Victoria of Hesse and Rhine and Prince Louis of Battenberg. The couple shared three other children as well as Louis - Louise - who became Queen of Sweden - George, and . was known to be exceptionally close to his uncle Lord Mountbatten, who is also believed to have introduced Philip to his future wife , then Princess.

Lord Mountbatten was a distinguished who fought at sea in World War One and World War Two and was even hand-picked by wartime Prime Minister as an integral planner for the bold D-Day invasion of June 1944. He took on important naval roles such as First Sea Lord, Chief of the Naval Staff, Admiral of the Fleet and Chief of the Defence Staff.

The royal famously served as a mentor for III, and created a very close bond with the monarch over his lifetime. The bond was so strong in fact, that Charles would later go on to give his first son and heir the middle name 'Louis'. Lord Mountbatten died aged 79 in August 1979. Three others died in the attack, including his 14-year-old grandson Nicholas Knatchbull.

Lord Mountbatten's funeral was held at and he is buried at Romsey Abbey in Hampshire, near his family home of Broadlands. The name Louis has been used to honour his memory ever since. William and Kate carried Charles's tradition by naming their oldest son , as well as giving their youngest son the same first name. Other royals have also used the name include , whose full name is Edward Antony Richard Louis, while has the name Louise as her fourth name. It is also believed that Edward's daughter is named after the late Lord Louis.