libel/defamation - general advice?

[redhatnoknickers]

Could anyone advise please: if someone were to be called as a witness in a defamation case, what kind of solicitor could advise them (which branch of law)? Does someone asked to give a statement by a defendant have to comply or should they wait to be subpoenaed by the court? Are they expected to attend in person or is a written statement sufficient?

[prh47bridge]

Why does the witness need legal advice? They are only being asked to say what they know.

If the witness is asked for a statement by either side they do not have to comply. However if the witness receives a witness summons they must turn up. They cannot simply send a written statement.