They included the Manchester Survivors Choir, made up of people who were at the arena on the night of the fateful concert last May 22, and Parrs Wood High School's Harmony Group, whose post-attack tribute went viral previous year.
One of the groups performing is the Manchester Survivors Choir, a group made up of those who were there on the night of the attack, and a local school choir that performed onstage with Grande at the One Love concert.
The 30-minute singalong in Albert Square featured...
As I said at the time of the attack, this was a despicable and evil crime which should be condemned by everyone.
Take That's Never Forget followed as members of the crowd embraced and held their hands in the air - before The Beatles' All You Need Is Love rounded things off.
Peter Byrne PA Wire PA Images AP FILE
The atrocity was one of a spate of terrorist attacks to hit Britain a year ago - the one in Manchester and four in London - that included bombings and deadly violence with vehicles and knives. "My heart is always going to be in Manchester", said Marr, "Always has been and always will be". We have at times become complacent to the evil of terrorism in some parts of our community; this is not good enough we should confront this evil and not hesitate to call out the actions of these evil people, their supporters and financial backers.
Along with Prince William and the prime minister, other dignitaries present included the Labour leader Jeremy Corbyn, Scotland's first minister Nicola Sturgeon and the Greater Manchester mayor Andy Burnham.
With his wife and father looking on, he paid tribute to the "amazing work" of the emergency services and those who responded on the night.
Earlier Manchester came together in an emotional day of remembrance, with 800 people attending an afternoon commemoration service at Manchester Cathedral while a one-minute silence - observed nationwide - was held at 2.30pm.
Bells on the city hall and churches will ring out at 10:31 p.m., exactly a year since the bomb exploded.
Twenty-two lit candles on the altar represented each one of the victims, which were made using wax from the thousands of candles left in St Ann's Square in their memory last May.
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