R v Paul Chambers (appealed to the High Court as Chambers v Director of Public Prosecutions), popularly known as the Twitter Joke Trial, was a United Kingdom legal case centred on the conviction of a man under the Communications Act 2003 for posting a joke about destroying an airport on Twitter, a message which police regarded as "menacing".

On 6 January 2010,[7][8][9] an intending traveller, Paul Chambers, then aged 26,[10] who was planning to fly to Northern Ireland to meet his then girlfriend (later wife), posted a message on Twitter: Crap!

Chambers was arrested by anti-terror police at his office,[9] his house was searched and his mobile phone, laptop and desktop hard drive were confiscated.

[11] He was later charged with "sending a public electronic message that was grossly offensive or of an indecent, obscene or menacing character contrary to the Communications Act 2003".

[19] Thousands of Twitter users responded by reposting Chambers' Tweet including the hashtag #iamspartacus,[20][21] in reference to the climactic "I am Spartacus!"

[27] He also asked whether Shakespeare would have been prosecuted if he had tweeted his line from Henry VI, Part 2 (Act IV, Scene 2), "The first thing we do, let's kill all the lawyers".

[6] The approved judgement concluded that "a message which does not create fear or apprehension in those to whom it is communicated, or who may reasonably be expected to see it, falls outside this provision [of the 2003 Act]".

The "grossly offensive" test has remained controversial and has been further reviewed by the Law Commission, which is examined offences to "improve the protection afforded to victims" while providing "better safeguards for freedom of expression".