A British man has won himself free pizza for a year after he pit the marketing departments of two British phone companies against each other on Twitter.

The 'hijack' of the marketing campaigns began when mobile company O2 offered its Twitter followers free pizzas delivered to their office.

All people had to do was reply to O2's message with their location and a hashtag, and a handful of lucky winners would get their hands on the pizza.

Naturally, Dan May gave it a go - but the promised pizza never arrived.

Disappointed, he Tweeted O2 again - threatening to switch to rival phone provider Three unless they made good on their pizza promise.

Three noticed his tweet, and picked up O2's slack, delivering a pile of pizzas and a hefty amount of ice cream to his office on the same day.

Not to be outdone, O2 went for the nuclear option - offering May free pizza for the rest of the year.

His pitting of the two mobile giants against each other was well-timed - a deal to merge Three and O2, which came after Hong Kong telecoms conglomerate Hutchison agreed to buy O2 from Telefonica for £10.5 billion, will go before European competition watchdogs next month.