As one cannot libel the dead then this interesting question can be reopened.
Lord McAlpine returned to priminence in 2012 after Twitter users, including Sally Bercow, the wife of the speaker of the House of Commons, wrongly implied he was the politician from the Thatcher era which Newsnight had implicated in allegations that boys were sexually abused at a children’s home in Wales in the 1970s and 1980s.
Newsnight did not name the politician, but during widespread speculation about his identity Mrs Bercow wrote on Twitter: “Why is Lord McAlpine trending. *innocent face*.”
Mrs Bercow later apologised and last October agreed to pay the peer £15,000 in damages. The BBC also apologised unreservedly to Lord McAlpine and settled his defamation claim for £185,000.
And of course it wasn’t Lord McAlpine at all.
However, there’s a certain blogging boat of all our acquaintance that has certainly claimed, in the past, to have known who it was. Be most interesting if this all came up again, wouldn’t it?