IN 1863, London became the first city in the world to build an underground train system. The line, which ran from Paddington to Farringdon, used coal-powered steam trains. For passengers, that made the daily commute a grimy and unpleasant one. Plus ca change, a modern-day Londoner might lament. Today’s tube network runs for an impressive 402 kilometres, through 270 stations. But demand has increased dramatically. In the 2015/16 fiscal year, Londoners took 1.34 billion tube journeys. That is two-and-a-half times more than in 1982, the post-war low point. Trains are often crowded and delays frequent.

Things have been improving recently. Much of the network of 11 lines that runs deep beneath central London’s streets was built in the 50 years after that inaugural journey (the exceptions being the Victoria line, which opened in 1968, and the Jubilee line, which opened in 1979; other lines have since been extended into the suburbs). So Transport for London (TfL), which runs the tube, has been busy overhauling its creaking infrastructure, upgrading signals (some of which dated back to 1920), tracks, trains and stations. It says it now invests £1.3 billion ($1.9 billion) a year in the network.

But there is one improvement that many still yearn for. On May 23rd Sadiq Khan, London’s new mayor, announced that the capital’s long-awaited all-night tube service will begin running in August, initially on two lines on Fridays and Saturdays. (It will eventually be expanded to five.) That will start to bring it up to speed with other 24-hour cities, such as New York, Berlin and Sydney.

That will be a boon to nightclubbers and shift workers alike. According to research commissioned by TfL, some 22,580 work the night shift in London on Fridays and Saturdays. Many are in low-paid professions such as catering, cleaning and security. As the cost of living in the centre of the capital has risen, many have been forced into the suburbs. For them the long journey home has often meant relying on London’s night buses, useage of which has increased by 170% since 2000. TfL says the night tube will save many over an hour on their journey time. It expects that some 180,000 journeys will be made on the underground each morning between 12.30am and 06.00am, around half of which will be new trips. The remainder will be made up of those switching from night buses, taxis and minicabs.

But overhauling inadequate infrastructure has only been half the battle. The unions that represent many tube workers have proved quick to strike whenever modernisation has been deemed a threat to its members’ cushy contracts. (A newly qualified tube driver typically earns £50,000 a year for a 36-hour week, and gets 43 days annual leave.) The night tube was originally scheduled to launch last September, but those plans were scuppered by industrial action by drivers who were seeking better pay. (They also cited safety concerns.) Some drivers have since agreed a deal, after a promise of bonuses, and TfL is currently training 200 part-time drivers to cover the service. But the unions are still spoiling for a fight. Just a day after the mayor's announcement, the National Union of Rail, Maritime and Transport Workers said maintenance staff had voted in support of further action against the launch of night-tube services. More disruption to the timetable seems inevitable.