The PCF80 is from the era of VHF Band III television. Band III television in the UK began in 1955, up to that date the only program was the one BBC channel. The Band III service was the start of commercial television.
The valve is a triode pentode, with separate cathodes, designed to function as a mixer and oscillator in the tuner.
The article referenced above gives details of the faults and performance of the PCF80.
Mullard also advertise the PCF80 as a video amplifier and cathode follower in a single envelope.
See alsoPCC84 for the corresponding pre-amplifier valve for Band III television tuners from the mid 1950s.
This view is looking along the length of the grids of the pentode section. The wide plate is the internal screen.
This view is looking straight at the triode, again the screen is the plate behind.
With the screen on the left we see here the triode end elevation.
The thin glass tube envelope is 20 mm in diameter and, excluding the B9A base pins, is 49 mm tall.
References: Datasheet & 1040. Type PCF80 was first introduced in 1953.