Defamation of character I suspect would be highly relevant, especially if you can demonstrate that being accused of something you haven't done - which relates to something on twitter - has had a negative effect on your employment or role in an organisation.
This would include being called in for a disciplinary even if no action was taken, because of the stress it might cause you.
But having to demonstrate you had been affected negatively is not necessarily a obstacle.
The big thing to prove if you went down this route was that you had been the victim of 'serious harm'.
en.wikipedia.org/wiki/Defamation_Act_2013
The Defamation Act 2013 (c 26) is an Act of the Parliament of the United Kingdom, which reformed English defamation law on issues of the right to freedom of expression and the protection of reputation. It also comprised a response to perceptions that the law as it stood was giving rise to libel tourism and other inappropriate claims.
The Act changed existing criteria for a successful claim, by requiring claimants to show actual or probable serious harm (which, in the case of for-profit bodies, is restricted to serious financial loss), before suing for defamation in England or Wales, setting limits on geographical relevance, removing the previous presumption in favour of a trial by jury, and curtailing sharply the scope for claims of continuing defamation (in which republication or continued visibility constitutes ongoing renewed defamation). It also enhanced existing defences, by introducing a defence for website operators hosting user-generated content (provided they comply with a procedure to enable the complainant to resolve disputes directly with the author of the material concerned or otherwise remove it), and introducing new statutory defences of truth, honest opinion, and "publication on a matter of public interest" or privileged publications (including peer reviewed scientific journals), to replace the common law defences of justification, fair comment, and the Reynolds defence respectively. However, it did not quite codify defamation law into a single statute.
The defences are on the wiki page and lie with the person who defamed to show that they had reason to believe (evidence) that you were indeed what they said you were.
the actual act here for more detail [[http://www.legislation.gov.uk/ukpga/2013/26/crossheading/defences/enacted]]
In this case, I would suggest this defence would not hold up well in court.
The actual text of the Defamation Act 2013 is here:
www.legislation.gov.uk/ukpga/2013/26/contents/enacted
The serious harm clause is here:
Serious harm
(1)
A statement is not defamatory unless its publication has caused or is likely to cause serious harm to the reputation of the claimant.^
(2)
For the purposes of this section, harm to the reputation of a body that trades for profit is not “serious harm” unless it has caused or is likely to cause the body serious financial loss.
I would argue that if you were 'likely to lose your job' from this or actually had would potentially be sufficient grounds (hence why being called in for a disciplinary even if no action was taken would be a big deal).
I'm not a lawyer nor have any legal training, so don't take my word for it. From this though, I'd say there might be reason to pursue this further and consult with an actual lawyer.
(FTW, I don't think I've seen much on MN that would class as defamation against Lily, simply because there is a very good defence in that its in the public interest because of the office and role Lily holds...)