Elisabeth Sladen was one of the very favorite Doctor Who companions. She died fifteen years ago, as I noted at the time.
Sladen’s final regular appearance as Sarah Jane Smith during the classic period of the series was in “The Hand of Fear”. The BBC has graciously made the 4-part story from 1976 — half a century ago! — available for free viewing.
Does UK TV from the time appear to have almost HD quality? That’s because it had 625 lines of resolution, compared to America’s 525 lines.