London Mayor Sadiq Khan has pledged to bring full 4G network coverage to the London Underground, meaning passengers can call, text, Instagram, Snapchat and more on their phones whilst travelling beneath the capital.

The plan is to have full coverage in place by 2019 and if it happens, it will mean London can effectively catch up to other cities around the world that already have mobile network coverage on their underground transit systems. Cities include Paris, Tokyo, Seoul, Amsterdam and New York.

Mayor Khan's pledge was delivered to all 33 London local authorities as part of an overall package of targets for London to meet. He said he wants "mobile connectivity on the London Underground, both in stations and tunnels by 2019, future-proofed ready for 5G."

Tenders for the contract to complete the task are said to be "going out shortly", and the Waterloo and City will likely be the site for testing. The line between Waterloo station and Bank is closed at night and over weekends, so will provide the best base for trials to take place.

The new Elizabeth Line, which will have its first journey in 2018, will launch with full mobile coverage services.

The majority of stations on the London Underground already offer Wi-Fi connectivity thanks to Virgin Media, but when travelling through the numerous tunnels, the signal drops out. 

Business leaders are said to be behind the plans, as having full network coverage will enable reliable connections for people when they're on the move, and not just at home or in the office.

However, for some it's not such a good thing, as it will eliminate the last real "not-spot" in London. Some people prefer having no signal as it forces them to not use their phone, and means they can't be contacted.