"Have you seen Soho at night?" he asks. "Imagine all those fights on the Tube. Someone's going to push someone on the tracks.

"I'm not worried about delays, I'm worried about people getting killed."

He also asks me to check out their digital advertising, especially created for the Night Tube's first night. I forget. But later I notice that supermarket chain Tesco's has bought some promoted Tweets, to point out that its stores have extended opening hours along the Night Tube routes.

"Night Tube, Night Tube."

1.52am, Oxford Circus. Two young women, arm in arm, are going along the platform and pointing at people then saying, in delighted voices, "Night Tube!"

"What are you on?" they ask me, narrowing their eyes.

"The Night Tube," I say.

Two men walk past.

"Night Tube, baby," one says to the other, but it doesn't sound the way it reads.

So far, nobody has died.

Instead, there's a party atmosphere on the Night Tube.

London has joined New York as a 24-hour subway city, albeit Fridays and Saturdays only, and so far just on two lines. A city that never sleeps, except on work nights, when it's still best to get a decent night's kip.

London is a city of traditions.

Two of those traditions died tonight.

The first is that familiar moment of panicking realisation that it's not 11pm, this is not only your second pint, but instead it's 12.30 am and you have about 5 minutes to catch the last Tube home, and you're not going to be getting to the station in a straight line.

The second, consequential tradition was the Night Bus. A queasy, chip-smelling world of angry conversations, drunk conversations, loving conversations, incomprehensible and slightly terrifying conversations, head-lolling drunks holding an anxious conversation with their rebellious stomachs. Best friends asleep on each other's shoulders.

It inspired movies and briefly even became a music genre.

No longer. As of Friday the Night Tube is here, every ten minutes on the Victoria and Central lines, all night.

As Time Out pointed out, it's going to seriously impact people's lives. For a start, a lot of them will be going home earlier (because they don't have to wait for the first tube at 5am).

And you'll need a better excuse to leave a lousy party.

But it's all in a good cause.

The Night Time Industries Association estimates London's night-time economy is worth £66 bn and employs 1.3 million people – mostly in hospitality and entertainment.

But it has recently hit headwinds.

In 2005 new licensing laws allowed 24-hour operation, but councils were wary of granting many such licences.

From 2013 to 2014 the number of 24-hour alcohol licences actually fell – with a near-10% fall in the number of pubs, clubs and bars with a 24-hour licence across the UK.

A recent study by the Institute of Economic Affairs showed that alcohol consumption has dropped by 26% in licenced premises and is down 17% overall since 2003.

The club scene was hardest hit. The number of UK clubs and live music venues has almost halved in the last decade, from 3144 to 1733 in 2015.

To add insult to injury, this year the Office for National Statistics took nightclub entry fees off their 'basket' of goods used to calculate inflation – along with CD-Roms.

There has been a recent plague of think pieces claiming, on mainly spurious, anecdotal evidence, that millennials are straight-laced stay-at-homes.

It's true that the number of teetotal Britons aged 16-24 has increased by 40% in the last decade. But the full situation is more complicated: young people have a bigger range of entertainment options after dark beyond pubs and clubs: from night markets, rooftop cinemas to Tinder. The Neil Cornelius hair salon on London's Bond Street takes appointments (though not walk-ins) at any hour.

This theory, that London's nightlife is maturing rather than shrinking, is borne out somewhat by the fact that since 2000 night bus usage in London has almost tripled. The city has never been more sleepless.

For the Night Tube, I was prepared for the worst. Staff flung vegetable soup around train carriages in a dress rehearsal for the launch of all-night services: a spokeswoman said they were testing how quickly "waste" could be cleaned up in the event of an "incident".

I see no vegetable soup.

At 12.50 a karaoke group gets our carriage singing All Night Long, in a transparently media-savvy setup.

"It's just like New York," says one excited passenger. Sorry, people, the Central Line to Notting Hill Gate is no L Train.

1.12am, four men wearing backpacks stage an endearingly halfhearted dance party in an empty carriage.

1.30am, the train east from Liverpool Street is packed. Francis, from Italy, says he's over the moon about the Night Tube. "Southern European people love to stay out until 5am," he boasts, on his way home.

People are taking selfies in front of the Night Tube logo. A young man pulls a high-vis vest from his backpack (shift workers are often cited as benefiting from the Night Tube). A gothic, pierced and black-clothed couple entertain themselves by celebrity casting a new movie, "Night Tube Sex Pest".

At Chancery Lane at 2am, four men swigging beer actually applaud the arrival of the train, and high-five as they get on board.

By 2.30 at Stockwell, half the carriage is asleep, and a group of three young women leave their shoes off as they alight at Brixton.

Back at King's Cross, a very skinny red-haired chap, topless except for a small backpack, sprints out of the station. Two men do an awkward skipping dance on their way to the taxi rank.

One of the immutable laws of buses and trains is that they only come along when you don't need them.

After three and a half years in London, the Night Tube arrives 12 weeks after I became a dad.