"Matt" wrote in message
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If you are referring to the hotchpotch 132kV grid that existed from
just before the second world war (1938?) then that is correct.
Before that was formed there were regional grids established from the
early 1930's, it was the interconnection of these grids by engineer's
operating overnight and out of sight of senior management that proved
the viability of a grid system. It was only experimental and as soon
as word got out the idea was quickly quashed only to be almost
immediately re-established as war broke out. Disruption of the grid
system during the war was substantial and so the country reverted to
regional grids during that time.

The national grid was planned as an entity from the beginning. It came into
being as a result of the 1925 Weir Report and the Electricity Supply Act
1926 set up the Central Electricity Board specifically to create and run
that grid, the last pylon of which was erected in 1933.

The BEA (i.e. nationalisation) came into existence in 1948 (following
the 1947 Electricity Act). However the fully interconnected grid
system as we now know it came into existence AFTER nationaisation.

That was primarily because the 1919 Electricty Supply Act had failed to make
Joint Electricty Boards compulsory and because the 1926 Act did not give the
CEB powers over the generation of electricity, beyond standardisation of
voltage and frequency. Until power generation could be centralised into a
relatively small number of large generating stations, there was no need for
anything better than the 132kV grid.

Colin Bignell