The UK’s second biggest mobile phone operator has revealed it will roll out its 5G network in October this year.

The super-fast service for O2 customers will be switched on in Belfast, Cardiff, Edinburgh and London first, with 20 towns and cities able to use 5G on the network from 2019.

Mark Evans, chief executive of Telefónica UK – O2’s parent company – said: “5G rollout will be prioritised in the areas where customers need the network the most, such as transport hubs and venues.

“Alongside O2’s work to build a 5G economy in partnership with British industry, we continue to focus on improving 4G mobile network connectivity as one of the UK’s most powerful opportunities to strengthen the economy and improve the lives of British people.”

Some of the first sites it will be available include Arsenal’s Emirates Stadium, Twickenham and Slough train station – not far from O2’s head office.

The news comes as the company revealed revenues in the UK jumped 5.1% in the year to £2.98 billion with underlying profits, the company’s preferred measure, up 6.4% to £919 million in the six months to June 30.

Bosses revealed that the O2 network was used by 33.3 million customers in the period, including via its services available on giffgaff, Tesco Mobile, Sky Mobile and Lycamobile. O2’s direct customer numbers is 25.4 million, the company added.

The number of customers in the UK on phone contracts has fallen in recent years, with users preferring to buy expensive handsets outright, before buying a sim card.

But O2 said net contract sign-ups were 41,000 in the period, accounting for 67% of its total mobile base. By comparison, there were more pre-pay sign-ups – with a net increase of 45,000.

On Wednesday, O2 also revealed a partnership with Vodafone to share masts and antennas to speed up their respective 5G rollouts and take on bigger rival EE.

Simon Neville is PA City Editor.