London is among the UK's worst cities for mobile coverage, with the capital coming 13th in a ranking of the country's 16 biggest metropolitan areas.

Data from mobile network tester RootMetrics shows that only three cities - Bristol, Hull and Cardiff - fare worse than London in the rankings of cities with populations higher than 500,000.

Belfast was found to have the strongest signal in an average of the UK's four mobile providers - EE, Vodafone, O2 and Three - despite having a population over 18 times smaller than London. The data, which covers the second half of 2016, showed London slipping from 10th place in the first half of the year.