New York has followed London by choosing hope over fear in electing Democrat Zohran Mamdani as its new mayor, Sir Sadiq Khan said.
Mr Mamdani, 34, defeated former New York governor Andrew Cuomo and Republican Curtis Sliwa to become the city's first Muslim mayor and the first of South Asian heritage.
London mayor Sir Sadiq drew comparisons to his own 2016 victory as he congratulated Mr Mamdani, who will become New York's youngest mayor in more than a century when he takes office on 1 January.
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Sir Sadiq called it a "historic campaign", adding on X: "New Yorkers faced a clear choice - between hope and fear - and just like we've seen in London - hope won."
Education Secretary Bridget Phillipson also congratulated Mr Mamdani, telling Sky News: "I wish him well.
"It's a wonderful job to have secured."
Green Party leader Zack Polanski said Mr Mamdani's success "will resonate throughout the world" as he called it a "story where no one is left behind".
"It's time to write that story across England and Wales too," he added.
Mr Mamdani's victory was a setback for Donald Trump, who had thrown his weight behind Andrew Cuomo, a former Democrat running as an independent.
The mayor-elect described himself as "Trump's worst nightmare" and said New York had shown "a nation betrayed by Donald Trump how to defeat him".
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The US president had threatened to cut federal funding to New York if Mr Mamdani won.
In his victory speech, Mr Mamdani said: "New York will remain a city of immigrants, a city built by immigrants, powered by immigrants and as of tonight, led by an immigrant.
"If anyone can show a nation betrayed by Donald Trump how to defeat him, it is the city that gave rise to him."
(c) Sky News 2025: 'Hope won': London mayor Sadiq Khan compares newly-elected New York mayor to his leadership
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