The operator’s parent group Telefonica today (8 May) reported that its UK arm added reached 12.2 million customers in the three months to 31 March, compared to 11.2 million twelve months earlier.

The operator also reported that its number of smartphone customers increased by 6 percentage points annually, accounting for 47 per cent of its customers during the period. This performance represented its best Q1 performance, in terms of customer additions, in four years – a period when it was still Apple’s official exclusive UK iPhone provider.

Q1 is a traditionally slow period for operators, but this was the first full trading period since the launch of its “design centre of excellence”, which aims to better integrate services such as Priority Sports into its offering.

The period also saw it step-up its Priority Moments drive by offering customers exclusive 48-hour access to tickets Beyoncé’s UK tour dates. See video.

O2’s total customer base grew 3 per cent year on year during the period to hit 22.9 million, with the operator reporting that its focus was on high-growth areas of mobile phone services.

However, the first quarter customer gains failed to translate immediately into revenue increases. O2 UK’s revenue fell 4.8 per cent year on year to €1,6bn during the period.

Although the operator did note the sharp annual dip in revenues was partly due to the impact of ending “mobile termination rate” charges, i.e. the fees it charged other operators for terminating calls on its network, after regulatory intervention.