The late Queen's decision to strip her son, Prince Andrew, of his HRH and military titles was a "final self-sacrifice".
According to a new documentary, it "showed she put the nation first" over her own personal connections.
The Duke of York was forced to step back from royal duties last year following a sex abuse scandal, which he denies.
He paid £12million in an out-of-court settlement to his accuser Virginia Giuffre, and was then blocked from appearing alongside the late monarch at the traditional Garter Day procession in Windsor.
The final episode of ITV's Inside the House of Windsor looks at Elizabeth II's close relationship with her second eldest son, who was often rumoured to have been her favourite child.
The segment, titled 'Heirs and Spares', explores how she maintained this relationship while devoting herself to the service of the British people.
A voiceover says: "Harry has left the country and builds a new life in America.
"And now, the Queen has stripped Andrew of his HRH title. A final gesture of self-sacrifice."
Following her death last September, Prince Andrew paid tribute to his "mummy", saying he will miss her "advice and humour".
The duke said in a statement: "Dear Mummy, Mother, Your Majesty, three in one.
"Your Majesty, it has been an honour and privilege to serve you. Mother - of the nation, your devotion and personal service to our
nation is unique and singular; your people show their love and respect in so many different ways and I know you are looking on honouring their respect.
"Mummy, your love for a son, your compassion, your care, your confidence I will treasure forever. I have found your knowledge and
wisdom infinite, with no boundary or containment. I will miss your insights, advice and humour.
"As our book of experiences closes, another opens, and I will forever hold you close to my heart with my deepest love and gratitude, and I will tread gladly into the next with you as my guide.
"God save The King."
Andrew accompanied his words with a black and white photo taken by society photographer Cecil Beaton of his mother holding him as a newborn in March 1960.
The duke was widely billed as the Queen's favourite son and someone whom she had a more hands-on relationship with than most.
During his time in the navy, he was was sent to fight in the Falkland Conflict as a 22-year-old and on his return he was greeted by his relieved mother as his ship as he arrived back in the UK.
Royal expert Katie Nicholl said: "He came back a hero and was very much the golden boy of the royal family."
He stepped down from royal duties in 2019 and the Queen later stripped him of his honorary military titles following the fallout of the Jeffrey Epstein scandal.
He lost his military roles, including Colonel of the Grenadier Guards, and he gave up his HRH style. But in the months before her death, he continued to be close by his mother's side.
