On 2 November, Newsnight broadcast what are now known to be mistaken claims by former care home resident Steve Messham that he had been sexually abused by a prominent 1980s Conservative politician.
Following the broadcast, there was much speculation as to who that politician was. Some of this discussion was via Twitter, with individuals linking Lord McAlpine to the Newsnight report - causing his name to appear as a "trending topic".
Media reports suggest that Lord McAlpine may be considering suing at least some of those thousands of people for libel.
The legal position of an individual who posts content online, be it on Facebook, Twitter, or on comment sections of online news pages, is clear: He or she is responsible for that content. Ignorance of the law is not a defence.
4 years ago