I didn't know very much about Black Orchid when I picked it up in the January sales - I vaguely remembered hearing that Peter Davison disliked it, but it was £3 and set in a country house in the 1930s, so I thought 'Why not?'

( Cut for spoilers; they are as mild as possible, but you can't analyse a whodunnit without talking a bit about the plot... )
All in all: I enjoyed it; it's not one of the Best Episodes of Who Ever, but it's a solid, enjoyable bit of work. Some people might find the pacing slow in the first half, but I rather liked it, and it's nice to see the big Tardis crew teasing each other - and Tegan being cheerful and enjoying herself...

Also, watching this made me very sad that Peter Davison never played Peter Wimsey, particularly "Murder Must Advertise" - it would have been so nice to have someone playing Peter who looked convincing as a cricketer and not fat and middle aged in a harlequin costume...