No sooner had EE announced an incentive for its customers than O2 follows with its own. O2 customers can now access free Wi-Fi throughout the UK without even having to sign in ever.

O2 Wifi Extra is the evolution of the network's free Wi-Fi service, which offers connection to hotspots placed in numerous locations around the UK, including inside McDonald's restaurants, Costa Coffee shops and the whole of Westminster, Kensington & Chelsea and Canary Wharf in London.

There are 11,000 locations across the UK that have O2 Wifi Extra hotspots and O2 customers will now be able to connect to them on their travels, without even having to open an app or signing in.

A customer with a compatible device - either smartphone or tablet - will automatically connect through authentication of his or her SIM card.

The service will also judge which is offering the strongest connection, the nearest hotspot or the phone's 3G or 4G signal, and use that one to give the best experience.

O2 also promises that the service is fully monitored and secure.

READ: It's official: Telefonica will sell O2 to Three UK's owner for £10.25 billion

"We are always looking for ways to help O2 customers stay connected, and delivering O2 Wifi Extra’s capabilities on such a large scale for our customers is a first for a UK public Wi-Fi provider," said Robert Franks, MD of O2's digital commerce business.

"It’s a great step forward for our customers. They’ll get the best data service available to them as well as being able to stay safe and secure online, wherever they may be."