Priory was a set of companies set up in the 1970s by Mortimus under the alias "Robert Betram". For one of the companies Mortimus invented the CD a decade early to prevent the Seventh Doctor from hearing Plasticine's performance (which had originally been a bootleg cassette). Priory also had access to a satellite in geostationary orbit called Skywatch.
Priory Records was another company, under whose label which Mortimus intended to release Plasticine's music. Following Mortimus' departure from Earth in 1976 the company went into liquidation. (PROSE: No Future)