While Prince Philip wasn't always close with his mother, she did write an emotional letter to him prior to her death.
Philip's mother, Princess Alice of Battenberg, was born at Windsor Castle in 1885 to parents Prince Louis of Battenberg and Princess Victoria of Hesse and by Rhine. Alice, who was one of Queen Victoria's great-grandchildren, was born with congenital deafness and learned to lip read, Tatler reported.
In 1902, Princess Alice met her husband, Prince Andrew of Greece and Denmark, at King Edward VII's Coronation. The pair married "at the Old Palace" in Darmstadt, Germany in 1903, "in the presence of a glittering assembly of 200 sovereigns, Princes, diplomats, and Cabinet Ministers," per The New York Times. They subsequently moved to Greece, and welcomed five children, of which Prince Philip was the youngest and their only son.
However, the family faced much difficulty when they were exiled from Greece in 1922. Mental health issues led to Princess Alice being "sent to the Tegel Clinic in Berlin" without her consent, per The British Psychological Society. Despite explaining she was "sane," Sigmund Freud and his associates "believed Princess Alice's religious delusions were the product of sexual frustration and recommended X-raying her ovaries in order to kill off her libido," the outlet reported. Following her treatment at the institution, "She did not see Prince Philip for some years and wandered round Europe incognito," The British Psychological Society noted.
After leaving Berlin, Alice returned to Athens in Greece, where she would found a school for nuns named the Christian Brotherhood of Martha and Mary, via Greek Reporter.
For the final two years of her life, Princess Alice lived at Buckingham Palace with her son, Prince Philip, and his family, per Tatler. She died on December 5, 1969 at the age of 84. But before she passed away, Princess Alice wrote a letter to Philip.
Even though they spent much of their lives apart from one another, Princess Alice expressed great emotion for her son in her final letter to him.
"Dearest Philip, Be brave, and remember I will never leave you, and you will always find me when you need me most," she wrote (via the Daily Mail). "All my devoted love, your old Mama."