As Sally Bercow is named as one of those expected to be the first to receive legal letters for allegedly defaming Lord McAlpine, Channel 4 News examines the chances for legal success over "Twibel".

Mrs Bercow (pictured, left) took to Twitter to say she would be seeking legal advice after it was reported that she would be among the first on a "very long list" of tweeters expected to receive a notice of legal action.

Solicitor Andrew Reid, who is representing Lord McAlpine, said the former Tory party treasurer would be sending a "letter before action" to the list of tweeters who mentioned his client on the micro-blogging website.

The former Conservative politician was wrongly linked to a child sex abuse scandal as a result of a Newsnight investigation. The action is being taken against those who allegedly tweeted his name in relation to the Newsnight programme. Lord McAlpine is in talks with the BBC over a settlement package in relation to the Newsnight episode.

Mr Reid said: "They will receive a letter before action, which I think is some 13 or 14 pages, and they will have 48 hours to respond, in the same way that we have dealt with the BBC, because the sooner this is dealt with the better for all parties," he said.

"It is a very long list. There are other broadcasters on it. We will be getting to them, but hopefully they will come to us, because it makes sense to do so. This is so vile, so disgusting, that it's easier to come and just get it over with. We want it over with as well."

The list includes Mrs Bercow as well as journalist George Monbiot, Mr Reid said. Also being pursued will be ITV's This Morning programme, Mr Reid said, after Phillip Schofield handed Prime Minister David Cameron a list of Conservative politicians that he had found on the internet. Ofcom said it would investigate the programme over the incident.

Mrs Bercow responded to to the news in two tweets on Twitter on Thursday afternoon:

Mr Monbiot has also used Twitter to emphasise his apology to the Conservative peer:

'Twibel'

Since 2011 Twitter and legal action have become entwined, with the first high profile court case being taken against singer Courtney Love. Ms Love paid £264,000 to settle the libel case over tweets she sent that accused a fashion designer of theft.

Libel cases on Twitter can be highly dependent on what information Twitter chooses to release. Twitter's policy on releasing private ionformation is that it requires "a subpoena, court order, or other valid legal process to disclose information about our users".

For requests for user information from law enforcement agencies outside the US, requests have to be issued via a US court by way of a mutual legal assistance treaty.

Despite the processes involved, Twitter has released private information in UK cases. In May 2011 Twitter released the details of an anonymous Twitter user to South Tyneside council. The council had gone through the Californian courts to force Twitter to release the details against a man accused of defamation.

However, this is only relevant when the Twitter user being pursued is anonymous. In cases of celebrities it is clearly easier to locate them.