Mourners were left "flabbergasted" as King Charles III left his official car to greet well-wishers outside Buckingham Palace.
The new monarch arrived in London from Balmoral following the death of his mother, Queen Elizabeth II. He later met with the prime minister and made his first address as King.
James Walmsley, from Liverpool, saw King Charles as he greeted the crowd at Buckingham Palace. "If you said 24 hours ago 'you're going to see the king' you'd never believe it but now we're here," the trainee teacher told The Independent.
"Seeing him made us all feel a lot more positive," the 23-year-old added. "My biggest concern was is the King going to be someone you don't see very often - just due to age?
"It's been a shame not seeing the Queen as much in the last 10 years as in years before, so it was nice seeing him get out of the car and walk around a bit, being active - it's a nice sign."
Civil servant Alastair from London said he only saw the back of King Charles's head and his foot but relished the moment as a "piece of history".
"Being here and seeing him was very monumental even though I just saw the back of his head. I feel very privileged to be here," the 54-year-old said.
"It was jubilant when he arrived, everyone was respectful and nice. There's been a sombre feeling but you feel the change with the new monarchy here and now we have a king - I've never had a king in my lifetime," he added.
Student Ash Moad said he was "flabbergasted" greeting the new King. "I could hear the crowd screaming when his car arrived, King Charles was in a car with Camilla herself," the 20-year-old said.
"It was crazy seeing him in person. Although he had a big smile on his face, everyone could feel he was very sad and low but he was still shaking hands and smiling.
"I didn't really get to see Camilla because the spotlight was on him [King Charles]. Before he came everyone seemed a bit sad and low but the mood changed when he arrived."
Ash added that he feels optimistic about King Charles as the new monarch but said he'll take time to settle into the role as he grieves his mother and father who died last year.
Virgin Active manager Ebbie Stout brought her three-month-old daughter, Vallie, to Buckingham Palace to allow her to be "part of history". She said she could only see the tops of cars because of the size of the crowds rushing to take pictures of King Charles.
When the King's state Rolls-Royce was first spotted by the crowds as it neared the palace, a cheer when up from well-wishers who had gathered in their thousands outside the gates of the royal residence.
One of the first to offer words of support to the new King was Laura Ohmona. After shaking hands with Charles, she said: "I said to him, 'sorry for your loss' and he said, 'thank you.'"
Charles smiled at the words of praise he received from the public and at several moments threw up his hands as if to say "thank you" when condolences were shouted out.
Josephine Bennett, 53, from London, exchanged a few words with the grieving King and said afterwards: "I said, 'we love you Charles' and he said, 'thank you very much'.
"This is all very surreal, but I'm so happy he's here, I wanted to see him."
From news to politics, travel to sport, culture to climate - The Independent has a host of free newsletters to suit your interests. To find the stories you want to read, and more, in your inbox, click here.