The new iPhone X boosted Dixons Carphone’s revenues in the run-up to Christmas, but the retailer said a tough mobile phone market damaged its margins as it confirmed the departure of chief executive Sebastian James this morning.

The electricals seller revealed group sales growth of 4pc for the 10 weeks to January 6 as its top line was boosted by a 28pc sales surge in its Greek division and 9pc growth in the Nordics.

But revenues in UK stores open more than one year were up just 3pc, compared with 6pc last year, and the company trimmed its full-year guidance, saying it would make a profit before tax of between £365m and £385m, down from a previous estimate of £360m to £400m.

Mr James, who will leave later this year to run chemist chain Boots, said he was “pleased” with the group’s overall performance but warned margins in its mobile phone business suffered due to "market conditions".

Nonetheless like-for-like sales in the mobile business, which includes its Carphone Warehouse stores, rose 8pc, thanks to the "phasing" in of the iPhone X, Apple's top-end handset, which costs £1,349 on the retailer's cheapest 24-month contract.