The whole Sherlock Holmes copyright thing is pretty confusing and very messy. A friend has suggested that I dig into it and write up an article about it, but whenever I try getting a grasp of the situation, my brain starts to hurt.
Hopefully the OP does not mind me continuing the hijack. Most of the SH stories are out of copyright worldwide. In the USA, this excludes ten of the twelve stories in The Case-Book of Sherlock Holmes which were published after January 1, 1923 and later had their copyright renewed. I forget the specifics of the UK and EU (and elsewhere?) but I think these stories are still in copyright there as well.
The website that jackdavinci quoted from is the self-proclaimed “Sir Arthur Conan Doyle Literary Estate.” Andrea Plunkett, through a means described on her website has claimed ownership of the copyright or trademark of all of the Holmes characters developed by Arthur Conan Doyle. She may also have claimed Challanger and *The Lost World[/]. The heirs of ACD have won every lawsuit they have brought against her and have even won the right to recoup legal costs, but last January Plunkett received a judgment that says she does not have to pay because she is too poor.
The various losses in court has not stopped her or her agent (Jonathan Cowles, Ltd.) from still trying to squeeze money from groups who wish to use the names of Holmes and his literary companions. (I think this is what may have stropped further episodes of Star Trek: The Next Generation dealing with Holmes, Moriarty and the holodeck.)
By and large, the Conan Doyle Estate (the proper one) didn’t mind the various pastiches, possibly because they realized they couldn’t stop them. The Estate was primarily ACD’s daughter, Dame Jean, and two daughters-in-law. They have all died and the Estate and remaining copyrights are controlled by a grand-nephew and similar relations of ACD’s. (None of his children had kids and so there are no direct descendants of ACD.)
Many pastiche writers do get permission from the Conan Doyle estate in order to lend an air of legitimacy to their work, but from what I have understood, and as has been clarified by others in this thread (and by the courts with Ms. Plunkett), it is not necessary.
In the USA there is the whole issue of derivative works which are restricted by copyright rules, but I don’t know how exactly this plays into the OP or subsequent questions. (Martini, you may want to get clarification on derivative works of copyrighted material in Australia before you start your Haggard series.)