Andy Lane's The Mahogany Murderers was my favourite Big Finish release of the whole of last year. Part of the Companion Chronicles sequence, which in theory bring back regulars from the first four Doctors to tell the stories of hitherto unheard adventures, it broke new ground in several ways: Henry Jago (as played by Christopher Benjamin) and Professor Litefoot (as played by Trevor Baxter) were never regular characters, but appeared only in the Victorian Sherlock Holmes pastiche The Talons of Weng-Chiang; the story itself doesn't feature the Doctor as a character; and it expanded the Companion Chronicles' normal two-handed format to include a third, barmaid Ellie as played by Lisa Bowerman (who was in the very last Old Who story and also has a long Big Finish career as Benny Summerfield; and has now directed all of the Jago and Litefoot stories bar The Spirit Trap).
So I gladly invested in the four new Jago and Litefoot plays from Big Finish (download or CD), even before I spotted that Big Finish had put some of their best writers on the case. And they are well worth it: The Bloodless Soldier by Justin Richards has werewolves, The Bellova Devil by Alan Barnes has Bulgarian vampires and a sinister London club, The Spirit Trap by Jonathan Morris has table-tapping and parallel dimensions, and The Similarity Engine, by Andy Lane who brought them back in The Mahogany Murderers, reprises the villainous Doctor Tulp (and signals that the next series is on its way). As Steve Mollman has pointed out, the plots aren't always totally coherent but the super performances of Benjamin and Baxter as the central characters, and of pretty much everyone else, make these a joy to listen to.
Unfortunately I can't work up the same enthusiasm for The Time Vampire, by Nigel Fairs, which brings back Leela and (for the first time in a Companion Chronicle) K-9 in the last story of a trilogy whose first two elements are The Catalyst and Empathy Games. I didn't really understand what was going on in The Time Vampire, though I liked it more than this reviewer did (again, I'm in agreement with Steve Mollmann), and will go back and listen to it again after I've finished my current revisiting of the Big Finish Gallifrey series which included Leel, both K-9s and both Romanas. (Apparently there's more of that on the way too.) It's a shame because Leela is one of my favourite TV companions, and does well both in spinoff novels and in the Gallifrey audios, but her Companion Chronicles have been less memorable.
Big Finish have been doing a run of stories with Colin Baker as the Sixth Doctor and Nicola Bryant as Peri Brown, starting with those that were commissioned for the original Season 23 before it was decided to do the Trial of a Time Lord storyline, and then reaching out into basically every available Sixth Doctor idea that had once crossed John Nathan-Turner's desk and was still retrievable. Colin Baker is gloating a bit because apparently this combined with the latest regular BF releases (see below) now means that he has starred in more Doctor Who stories, if you combine audio and TV, than Tom Baker or anyone else. Most of these Lost Stories have been about as good as the slightly better televised stories of the era (though the first, Mission to Magnus, is roughly as bad as The Twin Dilemma, the first Sixth Doctor story, which is regarded by many [including me] as the nadir of Old Who). These stories are much less moored in Who continuity than most Big Finish productions are, which reflects the difference in expectations between the mid-1980s Who viewer and the Big Finish's audio marketplace of today.
Of the last three, the first in order, Point of Entry, is by Barbara Clegg (who wrote the surreal and lush Fifth Doctor TV story Enlightenment) and has Christopher Marlowe, Aztec relics, a Spanish spy and astral travelling. Unfortunately it also has no regard for astronomical realities and not a lot of coherence, but it's a while before you work that out, probably because Clegg's outline was developed and implemented by Marc Platt who has yet to find a middle ground between genius and tedium.
The Song of Megaptera, by Pat Mills, features a giant space whale and has certain similarities to this year's Eleventh Doctor story, The Beast Below. It was originally proposed as a Fourth Doctor comic strip (Mills wrote the early great strips for Doctor Who Magazine as well as many other classic comics) and I felt would still have worked better as such; the story is OK but two of the guest cast, playing the captain and his first officer, really sound as if they are under sedation - bringing in moderately well known actors is only really successful if they can do audio (having said which, Susan Brown is excellent as the Chief Engineer).
Finally, Ingrid Pitt, better known as an actress who appeared twice in Old Who (in The Time Monster and Warriors from the Deep), also wrote a story called The Macros (plural of "Macro", ie inhabitants of the planet Macron) which slightly oddly bolts together some well-researched material on the Philadephia Experiment with a rather standard parallel-universe plot; again there is a good female guest actor, this time Linda Marlowe as Marcon's ruler Osloo, but I found myself distracted by my confusion between the (fictional) professor Tessler and the (historical) professor Tesla.
None of these three is as good as the two best in this series (Leviathan and Paradise 5, reviewed here and here) but none is embarrassingly bad either.
The main run of Big Finish audios has just concluded a Sixth Doctor mini-series, which began in City of Spires (reviewed here) with the Doctor encountering an aged Jamie McCrimmon in a very weird alternate Scotland. This plotline continued with a Companion Chronicle, Night's Black Agents by Marty Ross, starring Fraser Hines as Jamie telling the story of an encounter with a standard baddie in a standard haunted castle; really very skippable, and I dislike the Companion Chronicles veering from their original intention of covering the first four Doctors. But we're back in gear again with the next story, The Wreck of the Titan by Barnaby Edwards, which starts off on the Titanic, then abruptly shifts to the prescient novella of 1898, and then cuts to yet further stuff of legend and literature, setting up of course for a grand cliffhanger at the end. Finally Legend of the Cybermen by Mike Maddox brings back Zoe Heriot as well as Jamie, in a rather brilliant climax that steps outside the usual narrative (the scene set in the Big Finish studios was a particular touch of genius) and kept me guessing all the way through; I really can't say more than that without spoilers, but let's just say that if you know the best known of the Jamie/Zoe/Second Doctor stories you will love this one.
Finally, Solitaire by John Dorney brings back two interesting Who figures - Charley Pollard, a Big Finish companion created for their Eighth Doctor audios (and later getting a second run with the Sixth Doctor) and the Celestial Toymaker, voiced here by David Bailie, who was Dask in The Robots of Death but also did the Toymaker in Big Finish's resurrection of The Nightmare Fair earlier this year. I thought this was a brilliant two-hander, and I think it could be appreciarted even by Who fans with only a vague idea of Charley and/or the Toymaker; Charley is trapped in a peculiar toyshop and must work out what she is doing there, and indeed who she is. Continuity-wise it is set in her early days, before any later adventures in parallel universes etc, and is all the better for that simplicity. Great fun. I objected earlier to Companion Chronicles which do not feature the first four Doctors but I'll make an exception for this one.
In summary, the Jago and Litefoot plays are excellent and would be entirely accessible for listeners who know nothing of Doctor Who (though it would probably help if they listened to The Mahogany Murderers first; but it is also equally excellent and equally accessible). The Time Vampire requires detailed knowledge of Leela's story as seen on TV and then heard in The Catalyst, and is even then not very penetrable. The three Lost Stories featuring Colin Baker's Sixth Doctor are OK but not essential. Night's Black Agents is skippable but The Wreck of the Titan and Legend of the Cybermen are an excellent homage to Patrick Troughton's last season. And Solitaire is great as long as you at least know who the two main characters are.