During this period, Campbell maintained a connection with the Canterbury scene movement of which Egg had been a part, playing and recording as a support musician for Henry Cow, Hatfield & The North, Slapp Happy and others. Following graduation (and after a very brief stint with Alan Gowen's jazz fusion band Gilgamesh), Campbell linked up with Stewart again in 1975, this time as part of the original line-up of National Health, Although Campbell initially enjoyed his work with the band (for which he composed several pieces including "Paracelsus", "Agrippa", "Zabaglione" and "Starlight on Seaweed"), within a year he became disheartened by its lack of success. He left the band in June 1976 after a UK tour, a radio session for the BBC and a "disastrous" performance at a one-off French festival (the latter being his final appearance with the group). Although National Health secured a recording contract following his departure, Campbell's compositions would be dropped from the set: recordings of them would not surface until twenty years later on the archive collection "Missing Pieces".