The Black Digital Watch was a remarkable idea, but technically flawed. Its sleek design demonstrated Sinclair's interest in creating innovative tech which looked beautiful. A sleek black design  was punctuated by the red LED display.

The marketing campaign claimed there was 'nothing to go wrong' but the watch was riddled with problems.

It only displayed the time when the hidden button was pressed. This drained the battery quickly, despite adverts claiming it would last for a year. The watch was also susceptible to static, which made the display freeze on one very bright digit, causing the batteries to drain even faster. Overheating was also a problem. 

Launched in September 1975 by Sinclair Radionics, the Black Watch cost £24.95 ready-built or £17.95 as a kit. 

So many were returned it made a huge loss. Sinclair would have been bankrupted had the National Enterprise Board not stepped in to inject money into the company.

Video: Black Watch Advert

Image 1: Black Watch Kit

Image 2: A rare white version of the watch (CH 66646)