And the best UK mobile service is?

EE has again been ranked top overall in research comparing the performance of the UK's four mobile networks, with Vodafone coming last.

Research firm RootMetrics tested UK networks for the speed and reliability of their voice, data and text services in the first half of 2014.

EE was ranked first overall, followed by Three, O2 and finally Vodafone.

But RootMetrics said all networks showed signs of improvement compared with last year.

RootMetrics' research is based on more than 920,000 tests of the networks' services, conducted across the UK in the first six months of the year.