As part of an excellent essay on the role of the Nostalgia Factor in the Russell T. Davies (RTD) era of Doctor Who, Iain Clark makes many excellent points about both the new and the old series of Who, why Sarah Jane Smith was really the only choice as a returning former-companion for the new generation of Who-watchers, and the differing emphasis paid to character vs story in each.
Clark is writing what purports to be merely a review of the one episode of the second RTD season, yet by the end he’s engaging in an analysis of the entire Rose Tyler era in counterpoint to what we see of the characters in School Reunion.