EE has launched the UK's first next-generation 5G mobile network, with a concert by rapper Stormzy live-streamed from a boat on the River Thames.
5G mobile networks offer faster downloads, but customers will need a new handset to take advantage.
At first, the service will only be available in limited areas of Belfast, Birmingham, Cardiff, Edinburgh, London and Manchester.
Rival Vodafone plans to switch on its 5G service in the coming weeks.
EE's lowest-priced deal is £54 a month plus a one-off £170 fee for a compatible handset. But this only includes 10GB of data a month, which can be used up quickly if you download lots of movies or games.
On Thursday morning, BBC Breakfast had the UK's first live news broadcast over 5G.
Many news channels currently link several 4G connections together in order to stream video over mobile networks.
But using the 5G network, the BBC's technology correspondent Rory Cellan-Jones was able to broadcast in high definition using just one Sim card.
5G is not just about faster internet speeds. It also offers lower latency than 4G connections: that means less of a delay between sending a request and getting a response.
For Rory, that meant a shorter delay between hearing a question in his earpiece and answering live on TV.
One technical hitch delayed Rory's broadcast. Test transmissions had ploughed through the data allowance on the Sim card, so it needed a top-up before Rory could go live on BBC Breakfast.
That makes EE's 10GB data cap on its cheapest price plan seem a little bit limiting - although EE says the data cap was reached after several days of test transmissions.
Is 5G safe?
Analysis by BBC Reality Check
Some people have questioned whether there are health risks from 5G, but experts and regulators say there is no evidence of danger.
Similar fears were expressed around earlier mobile internet and wi-fi.
More than 200 scientists appealed to the EU to halt the roll out of 5G, saying that electromagnetic fields may be harmful to humans and the environment, and could increase cancer risks.
But the EU says exposure from 5G will be far below limits set by the International Commission on Non-Ionizing Radiation Protection (ICNIRP).
"There has been no evidence to suggest that electromagnetic waves from mobile phones and networks are bad for your health," says Prof Malcolm Sperrin, Director of the Department of Medical Physics and Clinical Engineering at Oxford University Hospitals NHS Trust.
He says a causal link between mobile phone use and cancer in humans is unproven.
5G technology is new but experts believe it poses no greater risk than earlier mobile systems.