The “Requirements For Electrical Installations” are otherwise called BS7671 or more colloquially as ‘the regs’.
This is a set of regulations which cover the selection, installation & inspection/testing of all electrical installations in the UK (with the exception of aircraft, boats, traffic lights & electricity supply networks). Basically, all the wiring in your home or business is (at least should be) installed to this standard, whichever amendment was in force at the time of installation.
The regulations cover design and safety elements which must be adhered to as well as capacities of certain fuses, circuit breakers and cables. There are also ‘special locations’ sections which cover locations such as bathrooms, swimming pools, building sites and medical buildings/areas (these locations have differing, more stringent requirements due to the increased risks encountered in these areas).
This is the main of rules which you would hear your electrician or electrical contractor refer to as the ‘regs’ or ‘big blue book’. The colour of the book changes with each edition so that it is easier to identify, thus the ‘big book’ changes every few years.
The edition of the regulations in force at the time of this article is BS7671:2008 (AMD3:2015). Whilst this might be a mouthful, in a nutshell: the edition was the 17th released in 2008. There have been 3 amendments since them, and the latest one, in 2015 was the 3rd amendment (yellow as a matter of interest!)
On the 1st July 2018 the 18th edition was released. This edition is blue! The regulations were released on the 1st July after a period of consultation, however compliance is required by 1st Jan 2019.