It starred Julian Bream, and he travelled about Spain discussing the musical heritage of each of the regions he passed through as well as the history of the Spanish guitar and its composers.
My favorite episiode was when he met Paco de Lucia. They sat down together and Paco belted out a few minutes of jaw-dropping flamenco guitar. Julian was obviously gob-smacked, and quipped, "looks like I better put some glue on my fingernails too!"

It has never been repeated on TV as far as I know

However, it is available from Amazon on DVD. Mine turned up today and I intend to devote most of thie week's evenings to watching it.
If you like classical guitar in any shape or form, this is a must-have! Bream himself gives some amazing renditions including my all-time favorite by Tarrega, "Recuerdos de la Alhambra".