BBC Programme Identifier
UNIQUE IDENTIFIER FOR BBC CONTENT
Packet Identification number; Packet identification number; BBC Programme ID; BBC PID
A BBC Programme Identifier (PID) is an alphanumeric, persistent, unique identifier for a television or radio programme brand, a season or series, or an individual episode, used by the BBC in their web URLs, iPlayer viewers, and internal databases. - this source erroneously expands the acronym as "Packet Identification number"