Landmarks No.8

The Highlanders.
Jacobites, pirate captains and duplicitous solicitors in 1746 Scotland. The last of the true historical stories which, despite being a regular feature in the first three years of the programme, had fallen out of favour with the production team by the time Patrick Troughton took over as the Doctor. (By true historical, I mean devoid of any fantastical elements - such as the "pseudo-historicals" in which a period or event in Earth's history is used as the backdrop to some alien activity).
Doctor Who had originally been intended as having a very strong educational element, and visits to Earth's history were an integral part of this (alternating with science-based adventures). It was no coincidence that the first two human companions were teachers of Science and History...
As time went on, the audience came to prefer monsters and alien planets, and the historicals began to lose their appeal. Interestingly, there was quite a bit of experimentation employed to make these stories more watchable - usually by the addition of strong comedic elements. Despite dark deeds and high body counts The Romans, The Myth Makers and The Gunfighters all have a great deal of humour running through them.
The historical stories just managed to make it out of the Hartnell era, and there wouldn't be anything similar until Black Orchid some 15 years later. (Though some would argue this isn't a true historical, in that the disfigured Cranleigh is used as a surrogate monster).

With their existence about to be consigned to the dustbin, we should be thankful that this particular historical story was made, as it introduces the young piper James Robert McCrimmon - arguably the second most popular companion of all time.
The partnership of Patrick Troughton's Doctor and Frazer Hines' Jamie is one of the best seen in the show - and should be used as a template for modern producers. You do not need to have impenetrable back-stories and unrequited love affairs - just a strong, loyal, funny and, above all, likable companion who travels simply because they want to.