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London CNN  — 

A huge new subterranean railway whisked fare-paying passengers deep beneath the streets of London for the first time on Tuesday as the UK capital opened a $25 billion new metro line that will transform travel across the city.

Large crowds of rail enthusiasts, commuters and excited locals turned out to catch the first of the new trains of the Elizabeth line as they departed from Paddington Station shortly after 6.30 a.m. Many had been lining up for hours.

The line, known as Crossrail before being renamed in honor of the British Queen – who visited it last week – will drastically reduce journey times across London. It’s the largest increase in the often traffic-snarled city’s rail capacity for half a century.

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Crowds lined up outside Paddington Station to ride the first trains on London's new Elizabeth line.

Its construction – an engineering marvel fraught with the hazards of burrowing around London’s existing underground tangle of Victorian tube lines, sewage pipes, building foundations and ancient burial grounds – has not been without controversy.

Originally due to open in 2018, the railway, at times Europe’s largest infrastructure project, has been beset by delays and an escalating budget. A question mark also hangs over how useful it will be after Covid drastically reduced commuter traffic.

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Light at the end of the tunnel: Crossrail was Europe's largest engineering project at the height of its works.
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Precision drilling: The project has seen new tunnels bored under central London, dodging archaeological remains and the London Underground system.
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Swanky: Crossrail's modern stations are a step up from most of London's Tube network.
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Cross rail: The project has been beset by delays and over-expenditure, leading London Mayor Sadiq Khan to express his anger.
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Deeper underground: The Paddington stop is dug below the current railway station.
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Face lift: Farringdon has been completely redeveloped to accommodate the massive increase in passengers.
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Smart work: The Elizabeth Line will slash journey times under the capital.
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Below decks: Tottenham Court Road will pitch Crossrail riders into the heart of London.
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Transformation: Whitechapel, in East London, will become another transport hub.
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Spectacular: The new Canary Wharf station was designed by Sir Norman Foster.
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The great outdoors: Only part will be underground. Outside Central London, the trains will run above ground.
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Pretty in purple: The new Elizabeth Line has its own color scheme and in-cabin design.
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Going green: The Canary Wharf station has far more than trains -- there's even a roof garden.
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Suitably swanky: The below-ground Paddington stop is a suitably spectacular addition to the 19th-century railway 'cathedral.'
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Semi-subterranean: The Paddington Crossrail station is sunk into the ground beside the current railway station.

But for those using the service on its first day, there were few concerns as passengers luxuriated in its spacious air conditioned train carriages, beautiful airy stations and smooth motion – a world away from the cramped and noisy experience of older underground lines.

Among the first was Elizabeth Harding, 37, a health service employee from the town of St. Albans, north of London, who rode the shiny new rails wearing special “Elizabeth line” sneakers after leaving home at 3.30 a.m.

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London Mayor Sadiq Khan pretends to mop his brow with relief as the first Elizabeth line trains leave on time.

“I like trains and my name is Elizabeth, and I’ve got the shoes, so I had to come,” she told CNN on the wide platform of Farringdon Station as a train glided quietly away to its next destination.

“How often are you going to get the chance to be part of a brand new train line opening in London?”

‘Trials and tribulations’

Barry Neild/CNN
Elizabeth Harding: "It's smooth, quiet and aesthetically pleasing."

Harding said the line lived up to expectations. “I think it’s smooth, quiet and aesthetically pleasing,” she said. “I particularly like the seat fabric – it’s beautiful.”

Will Folker, a 24-year-old London-based rail enthusiast who works in sales, also rose early on Tuesday to be among the first passengers. “It’s one of the biggest railway openings in the UK for quite some time, so I’m very excited to see it opening after all the trials and tribulations,” he said.

Barry Neild/CNN
Harding's Elizabeth line-themed footwear.

Folker also praised the experience of riding the new line. “It’s smooth, easy to use and it’s punctual. It’ll make things easier for people coming into central London.”

London’s mayor, Sadiq Khan, who spent Tuesday morning traveling the new line and happily posing for selfies with customers and staff, spoke of his delight at the line’s long-awaited launch.

“Everyone should be so proud,” he told reporters at Woolwich station in southeast London. “We have the world’s finest railway opening to the public.

Leon Neal/Getty Image
The Elizabeth line's distinctive seat coverings.

“The last time we had a transport expansion on this scale was in 1969 when the Victoria line opened.”

The line was hit by one minor setback on opening day when an accidental fire alarm triggered a precautionary evacuation of passengers at Paddington, causing minor disruption to late-morning journey times.

View this interactive content on CNN.com

When running normally, Tuesday’s opening saw trains connecting Paddington in west London with Abbey Wood in the southeast, with stops at key stations including the shopping center of Tottenham Court Road and the financial district of Canary Wharf.

And when it opens fully later in 2022, the 62-mile network will also connect far-flung commuter towns, bringing another 1.5 million people within 45 minutes of central London, and Heathrow, the UK’s main international airport.

Ben Jones contributed to this report.