The first new mainline station has opened in London for over a decade.
Services from Brent Cross West will run to St Pancras, with journeys taking as little as 12 minutes.
The Mayor of London officially opening of the station at an event on Sunday and veteran broadcaster Tony Blackburn became its inaugural announcer.
The £419 million station was due to take place in 2030, but was brought forward to put infrastructure in place before thousands move into new homes.
Direct Thameslink services will run to Luton Airport Parkway and Farringdon, providing a link to the Elizabeth line.
Six trains will run every hour on weekdays and Saturdays, with eight at peak times.
The new station is a 20 minute walk to Brent Cross Shopping Centre
Mr Khan said: “It’s really exciting that we have the first mainline station in London in more than 10 years.
“What this station does, it makes the possibility of the West London Orbital more likely… if we get the capital funding from the government next year and subsequent years.”
The Orbital is a proposed extension to the London Overground that would use existing rail lines running from West Hampstead and Hendon towards Hounslow.
Transport across London has been hampered by several problems this week, including grounded flights at Gatwick on Saturday related to air traffic control and Elizabeth line services stuck for hours near Paddington on Thursday.
Mr Khan said: “I’m really disappointed about how the failures of Network Rail have led to problems on the Elizabeth line.
He said it “shows the consequences of years of underinvestment”.
“It’s really important that Network Rail works closely with TfL and MTR. I’ve written to the chief executives of all three organisations explaining that Londoners and others deserve better.”
Services from Brent Cross West started earlier in the day before the official opening, with the first due around 7am arriving 20 minutes late to crowds of train enthusiasts who had gathered for its arrival.
“Start as you mean to go on,” Barnet Council leader Barry Rawlings said.
Speaking on the station, he added: “It’s a doorway to what will be a new town – a real statement of a place moving forward, looking to the future and expecting great things to happen.
“The plan is, I think, to have about 25,000 people working here, which is why we need a new station.”
He said buses would take visitors to the nearby Brent Cross Shopping Centre.
The Zone 3 station was built by contractor Volker Fitzpatrick, and it is one of the first stations in England to be delivered entirely by a local authority.
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