A man who was convicted and fined for tweeting that he planned to blow up an airport will take his case to Britain's High Court in a test of the limits of free speech on the Internet, his lawyers said Monday

Attorneys for Paul Chambers said prominent human rights lawyer Ben Emmerson has been instructed to lead the legal challenge to Chambers' conviction.

Chambers, a 27-year-old trainee accountant, was arrested in January after he posted a message on Twitter saying he would blow Robin Hood Airport in northern England "sky high" if his flight, due to leave a week later, was delayed.

Chambers insisted it was a joke. But a judge found him guilty of sending a menacing message over a public telecommunications network and ordered him to pay a 385 pound ($615) fine plus legal costs.

Earlier this month another judge rejected Chambers' appeal.

The verdict caused a wave of outrage on Twitter, with thousands of supporters retweeting Chambers' message with the tag "I Am Spartacus" - a reference to the 1960 movie epic in which the titular hero's fellow rebels all assume his identity in a gesture of solidarity.