Fifty-two thousand petals fell in St Paul's Cathedral as families and survivors remembered those who died in the 7 July terrorist attacks in London 20 years ago.
Four bombers targeted three Tube trains and a bus in 2005 in the worst single atrocity in Britain, killing 52 people and injuring hundreds more.
The daughter of a woman who died near King's Cross broke down as she read out her mother's name during the memorial service.
Saba Edwards's voice cracked as she started reading the names of those who died, and when she got to her mother Behnaz Mozakka's name, she began to sob and had to briefly pause.
Thelma Stober, who survived the Aldgate bomb, took over reading the names, but her voice also strained.
The petals landed on the heads and shoulders of the congregation, who did not brush them off, before the cathedral fell into a minute of silence.
Four candles representing the site of each attack were carried through the cathedral by members of the emergency services and placed in front of the altar.
Readings were given about the history of each of the parts of London that were targeted in the attacks.
Ellie Patsalos, wife of survivor Professor Philip Patsalos - who was around three feet from the bomb that went off in a train between King's Cross and Russell Square - read the first passage.
This was followed by readings from Tony Silvestro, an emergency responder from British Transport Police who was called to Aldgate; Reverend Julie Nicholson, mother of musician Jennifer Valda Ann Nicholson who was killed at Edgware Road; and George Psaradakis, the driver of the bus that was blown up in Tavistock Square.
Please use Chrome browser for a more accessible video player
A conclusion was then read by Graham Foulkes, father of David Foulkes, who died at Edgware Road.
He said: "When four bombs exploded on 7 July 2005, lives were destroyed and the flame of hope faltered for what seemed like an eternal moment.
"For many people nothing was the same again and yet everything was the same because the good which is in Londoners and the countless visitors whom they host at any given moment is not erased by hatred or threat but rather is fostered to produce a harvest of hope for each generation."
The 1,200-strong congregation included bereaved relatives, survivors and emergency workers who were there on the day.
Read more:
Stories defining bravery of London attack victims
'I was reporting in London on day of 7/7 bombings'
Prime Minister Sir Keir Starmer, London Mayor Sir Sadiq Khan, the Duke and Duchess of Edinburgh, and Home Secretary Yvette Cooper were among those who attended the service.
The prime minister and Sir Sadiq also laid wreaths at the 7 July memorial in Hyde Park at 8.50am, to coincide with the time the first bomb went off.