King Charles told parliament on Monday he was "resolved faithfully to follow" the example set by his mother, Queen Elizabeth, addressing lawmakers and peers in what he described as the "the living and breathing instrument of our democracy".
At a ceremony in Westminster Hall, the oldest building on the parliamentary estate, Charles used his address to the upper and lower houses of parliament to pay tribute to his mother and to pledge to uphold the principle of constitutional government.
"While very young, her late Majesty pledged herself to serve her country and her people and to maintain the precious principles of constitutional government which lie at the heart of our nation. This vow she kept with unsurpassed devotion," he told the assembled lawmakers and peers.
"She set an example of selfless duty which, with God's help and your counsels, I am resolved faithfully to follow."
"As Shakespeare says of the earlier Queen Elizabeth, she was 'a pattern to all Princes living'."
The queen died at home on Sunday on Thursday, triggering a period of national mourning when tens of thousands of Britons are expected to pay tribute to her.
The ceremony at Westminster Hall, when the speakers of the House of Lords and House of Commons offered their sympathies to the new king, Charles also paid tribute to parliament as "the living and breathing instrument of our democracy".
"As I stand before you today, I cannot help but feel the weight of history that surrounds us, and which reminds us of the vital parliamentary traditions, to which members of both Houses dedicate yourselves with such personal commitment for the betterment of us all."