Grande also ushered in artists like Little Mix and Imogen Heap, while Stevie Wonder was featured in a video segment where, while strumming his keyboard declared, "Love is truly the key, I don't care what ethnicity you are, what religion you are". "Especially in moments like these, right? All we feel here tonight is love, resilience, positivity", Williams said before he launched into his hit song, "Happy" with an assist from Miley Cyrus. "It's our greatest power". Olivia wouldn't have wanted me to cry. "I had more reservations than my daughter - I feel that I can't stop her from living the life she wants to live".
Grande closed the show by inviting all the other performers on stage to help her sing her 2014 hit One Last Time, before she closed with a moving solo version of Somewhere Over the Rainbow.
Grande said she had not planned to play so many of her big hits but changed her mind after meeting the mother of Olivia Campbell-Hardy, 15, who was among the victims of the blast that killed 22 people at at her concert last week.
Perhaps the most emotional moment early in the evening came when Grande performed with a children's chorus, the Parrs Wood High School Choir, after which she appeared to choke up. And shop all the One Love Manchester merch here.
50,000 people crowded into the Emirates Old Trafford to pay tribute and raise money for the victims of the Manchester Arena bombing on 22 May.
FILE - In this Thursday, May 25, 2017 file photo, Marcus Mumford of the band Mumford & Sons performs in concert during their "Wilder Mind Tour" at the BB&T Pavilion in Camden, N.J. Mumford is joining the all-star lineup for Ariana Grande's "One Love Manchester" benefit concert Sunday, June 4, 2017. We must not be afraid, and in tribute to all those affected here and around the world, we will bring our voices together and sing loudly. Tears could be seen the corner of Justin Bieber's eyes as he reminded the thousands watching across the world that God was looking for them and the families of those who lost loved ones.
"Manchester, we're gonna be all right", she yelled.
After Saturday night's events in London, Lily Garner, 22, said she felt some trepidation about coming to Sunday's concert, but that she ultimately overcame it.
"We were lucky we weren't hurt", they told us.