In 1978, while Philips and Sony were still trying to agree a standard for CD, Matsushita’s subsidiary JVC unveiled the VHD/AHD system. VHD stood for Video High Density. AHD was the digital audio version, with coding quality to match CD. JVC’s VHS Division was not pleased, believing tape to be a better bet than disc.

AHD relied on a 10in disc like a groove-less LP. It was pressed from conductive plastics, with a spiral of tiny pits tracked by an electrode stylus which sensed changes in capacitance. Any dirt, dust or finger print contamination made the disc unplayable. So it had to be protected by a bulky caddy.

Despite all these painfully obvious disadvantages, Thorn-EMI backed the system in 1980, built a factory in Swindon to press discs and announced ‘firm’ launch plans for Japan, the US and UK.

In November 1983, a full six months after the UK launch of CD, Thorn-EMI was still sending out circulars to the trade quoting prices for AHD pressing. Thorn-EMI then dropped the project and wrote off £20m. The Swindon site was later converted to CD pressing.

In Japan, JVC doggedy continued to develop AHD technology right through the mid-Eighties, long after CD had become a hit. The final format offered up to four digital audio channels, with the option of high quality still pictures, or the whole disc could be used for up to 2.54 GB of computer data.

AHD went on sale in Tokyo in November 1985 – three years after the Japanese launch of CD. The player cost over £1,000 and came with five free discs, a mix of documentaries and soft porn. As two hours of music played, 3,000 high quality still pictures appeared on the screen of the TV set. There were few takers.

In 1994, the BSI issued a British Standard to cover the dead format.