The idea of 2 core leads and extra insulation to give double fault to danger was sort of out there long before they were called that by the IEC - and they created the formal  classes I and II we know from 1969 onwards, and at about the same time classes 0 (single insulation no earth )and 0A (single insulation and earth by separately  installed flying lead only) were generated to cover less safe existing kit as well, but then immediately deprecated. (still commonly found  in developing world however).

Black and Decker had a formal 'DI programme' in the early 1970s, re-modelling their range of drills, saws etc to the new standards, but companies like Morphy Richards had been making what we would consider all-insulated hair dryers for some time by them - for example  the HDA 2 (Hair Dryer All-insulated model 2) is a 1950s beast. There may even have been an HDA 1 before it, there was certainly an HDA3 in the early 1960s.

However some of these pre 1969 products were sort of only halfway there, and used non-metallic screws and funny things like that, which nowadays would not be considered OK.

Mike.

Thanks Mike, much appreciated.

To quote from the foreword of BS 2754 : 1976 - Memorandum. Construction of electrical equipment for protection against electric shock :

'When this memorandum was first issued as BS 2754 : 1956 its purpose was to explain the principles and requirements for the, then, new constructional method of double insulation.'

The concept of double insulation as a method of protection against electric shock has therefore been around from at least the mid 1950s onwards.

mapj1 said:

The idea of 2 core leads and extra insulation to give double fault to danger was sort of out there long before they were called that by the IEC - and they created the formal  classes I and II we know from 1969 onwards

It was introduced in the UK much earlier than that acknowledgement ... in the 1950s.

The first double insulated Hoover vacuum cleaner in the UK, the 1224 (double insulated version of the Class I 119) was introduced in1957. Many "119" machines were later converted to Class II during repair and refurbishment - however, I doubt this was "legitimate", and there were certainly physical differences (apart from simply the lack of the protective conductor, and sleeving over certain live conductors).

Ross Currie said:

'When this memorandum was first issued as BS 2754 : 1956 its purpose was to explain the principles and requirements for the, then, new constructional method of double insulation.'

Yes, I believe that this was the first acknowledgement in a standard that became what we now know as "IEC 61140".

I was not aware of that one - I was aware of  it pre-dating the IEC classes but not by more than a decade. (makes the B and D campaign  quite late actually - I have since found this amusing read.  Double Insulation The Black & Decker Story (PDF) )

Odd perhaps that we did not retain 2 pin sockets, had double insulation been a little earlier, or 13A plugs a bit later,  we may well have, as the idea of a compulsory CPC to each socket circuit only really appears in the post war regs. (to be followed less than 30 years later by CPCs in lighting circuits as well.)

Mike.