King Charles III addressed his nation for the first time on Friday, vowing to emulate his late mother Queen Elizabeth’s “life-long service” as Britain began a period of national mourning.

The new monarch’s words came at the end of day of parliamentary tributes, gun salutes and raw emotion, as thousands of people gathered at the gates of Buckingham Palace to leave floral tributes to Elizabeth II, some in tears.

“Queen Elizabeth was a life well lived, a promise with destiny kept and she is mourned most deeply in her passing,” the King said in his first national address.

Echoing the pledge made by his mother before assuming the throne, the King promised “life-long service . . . Whatever may be your background or beliefs, I shall endeavour to serve you with loyalty, respect and love.”

The King said he was bestowing the title of Prince of Wales on his son and heir, William, and expressed his profound sense of loss following the death of his “darling mama” at Balmoral Castle in Scotland on Thursday.

“Thank you for your love and devotion to our family and to the family of nations you have served so diligently all these years,” he said of his mother. “May ‘flights of angels sing thee to thy rest’.”

On Saturday, Charles III will be officially “proclaimed” king at an accession council in London, a constitutional formality to recognise his sovereignty attended by members of the privy council, which includes senior politicians and clergy.

King Charles arrived in London from Balmoral in the early afternoon and ordered his car to stop outside Buckingham Palace, in a sign of his desire to strike an immediate bond with his people.

He shook hands and exchanged words with scores of his new subjects to cries of “God Save the King”.

The new king, heir to the throne for 70 years, is now at the centre of a painstakingly choreographed series of events, encompassing 10 days of national mourning and the funeral for the Queen, widely expected in Whitehall to be held on September 19.

On Friday afternoon, King Charles held his first audience with Liz Truss, Britain’s new prime minister, who arrived in black at Buckingham Palace for a highly symbolic moment in the life of the nation.

Truss became Queen Elizabeth’s 15th prime minister at Balmoral only three days ago, succeeding Boris Johnson.

Parliament gathered at noon for a 10-hour session for MPs to pay their respects to the Queen while bells tolled at St Paul’s Cathedral, Windsor Castle and Westminster Abbey.

Truss told MPs the Queen was “one of the greatest leaders the world has ever known”, while Sir Keir Starmer, Labour opposition leader, said her death “robs our country of its stillest point, its greatest comfort”.

Johnson said the Queen had been “as radiant, knowledgeable and fascinated by politics” as he could remember during their final meeting on Tuesday, when she “saw off her 14th prime minister and welcomed her 15th”.

A service of prayer and reflection was later held at St Paul’s Cathedral in London, where mourners delivered the first official rendition of God Save the King.

The new monarch said he would now step back from the many charities and causes he had supported as Prince of Wales, an acknowledgment that as King he will have to steer clear of politically contentious issues.

Elsewhere, plans were made for the new monarch’s features to appear on the nation’s coins, stamps and post boxes; Queen’s Counsel at the bar will now become King’s Counsel.

Some sports events, including Premier League football matches and Test cricket, were cancelled as the period of national mourning began. The next meeting of the Bank of England’s monetary policy committee, due to be held next Thursday, was postponed until the following week.

London retailers Selfridges and Liberty closed their doors, music was stopped in Wetherspoons-owned pubs, and sporting and corporate events were cancelled across Britain as businesses paid their respects to the life of Queen Elizabeth II.

On a day of tributes, Emmanuel Macron, France’s president, captured a global sense of loss: “To you, she was your Queen. To us, she was The Queen. To us all, she will be with all of us forever.”