The Duke of Cambridge had no choice but to miss his youngest child's milestone because of an official trip to Christchurch, New Zealand in the wake of the terrorist attacks at Al Noor Mosque and Linwood Islamic Centre on March 15 which left 50 people dead.
Kensington Palace issued a statement confirming Prince William will begin his visit in Auckland followed by a day in Christchurch to meet with survivors and their families as well as emergency services who were at the scene of the atrocities.
The Palace said the Duke's presence is designed to "pay tribute to the extraordinary compassion and solidarity that the people of New Zealand have displayed in recent weeks".
William is taking the trip on behalf of his grandmother Queen Elizabeth who celebrated her 93rd birthday on Easter Sunday.
Kate Middleton reportedly held a low key early celebration for little Louis so William could be present, according to Hello! Magazine.
To mark the little Prince's big day, the Cambridges shared a series of stunning shots taken by amateur photographer Kate playing in the garden of their country home, Anmer Hall.