The Mayor of London arrived at St Clement's church in north Kensington as worshippers gathered to remember those who lost their lives and those who remain missing after the devastating fire.
Flowers and missing persons posters were taped to the gates of the church, while bags of donations were piled outside the door.
After having spoken to many members of the congregation as well as others who came in after the service to see him, Mr Khan paid tribute to the local community for its resilience but said a feeling of anger remains.
Speaking as he left the church with his wife Saadiya, Mr Khan said: "I've spent time with the local community, not just the Christian congregation, but members of all faiths here at the church, grieving, sharing their stories.
"And I've got to say some of the stories that I've heard will stay with me forever.
"I've heard stories of heroism, from Christians, from Muslims and from others, looking after their brothers and sisters, their neighbours and doing the job that we expect from this brilliant community because of the fantastic community that is here in this part of London."
He said people were "angry not simply at the poor response in the days afterwards from the council and the Government, but the years of neglect from the council and successive governments".
He said there was a feeling among people they have been treated badly and not understood by the council because some of them are "poor, some may come from deprived backgrounds, some may be asylum seekers and refugees".
"There's a feeling that the council and successive Governments don't understand their concerns and frankly don't care."
He added: "To those who think rules, regulations, health and safety, investment, are a bad thing, I say come to Grenfell Tower.
"Come and meet the wonderful people that I've met. Or remember those who have lost their lives in a preventable accident that didn't need to happen.
"The tragedy we're seeing is because of the consequences of mistakes and neglect from politicians, from the council, and from the Government."
Families who have lost their homes must be supported, he said, grieving people must be helped and lessons must be learned following the tragedy, including ensuring it is not "so hard" for those who need help to find it.
He said: "As the mayor of London I will do my bit to be the advocate, to be the fighter, and to be the champion of these people."
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