I love this episode, however have fought shy of writing about it because it manages to pack so much in, viz.
1. The Hammer style beginning. I actually think it is one of the nicest Avengers imitations of other genres.
2. Actually perhaps it's more in the style of Amicus because it is set in the present day and includes dialogue about the reality or otherwise of ghosts. I love the Avengeresque acronyms of the two ghost investigating groups, FOG and SMOG!
3. The episode is set against the noblesse oblige background of the Benedict estate. Very classic Avengers setting of the great and the good gone wrong.
4. The caricatured British setting is influenced by a very stereotypical foreigner.
5. It isn't explicitly mentioned but the noblesse oblige setting is not totally beneficent to the workers. The Benedict family not only formerly operated a mine, never a very safe or pleasant place to work, but the operation was brought to a close by an accident. However the dukes of Benedict are definitely not nouveau riche ennobled by Queen Victoria because they have got up to the sixteenth Duke.
6. It segues into (needless to say) a tale of megalomania and the aristocracy gone off the rails.
I honestly don't know why the reviews are mixed on the internet - what's not to love? I can see that the sheer volume of stuff included can be a criticism in itself and there are lists of problems with continuity. However as I keep saying, these showd were not expected to have the sort of scrutiny they now get. In fact the rather fake quality of the sets and props is surely part of the Avengers thing of deliberately not being realistic. The virtue then is in the frankly incredible nature of these shows.
Steed and Mrs Peel are very flirty, and she saves him from a firing squad. Again I am firmly of the opinion that any suggestion of attraction or sex between them isn't real. Despite a reproduction range of Avengers fashions being sold, surely it was only in the sixties that you could dress like an Avenger. Unreal in fashions as in everything else!