A man fined for a "menacing" tweet is the victim of a legal "steamroller", it was argued at the High Court.

Paul Chambers, 27, did not think anyone would take seriously his threat to blow an airport "sky high".

The accountant sent the tweet in a moment of frustration after Robin Hood Airport, South Yorkshire, was closed by snow in January 2010. But Doncaster magistrates fined him £385, with £600 costs, for sending "a message of a menacing character". Yesterday he asked the High Court to overturn Doncaster Crown Court's decision from last November upholding his conviction and sentence – which pushed the costs against him up to £2,600.

His lawyer, Ben Emmerson QC, said the questions were "whether this prosecution-conviction-sentence was a steamroller to crack a very small nut and whether it was a disproportionate response".

The judges reserved judgement for a future date.