What is this flattened tube coming down from the attic?

[Murdochcat]

That refers to sockets (not switches) but the distance is measured from the edge of a bath or shower - and has recently been reduce from 3m. to 2.5m.

No one knows why.

Minor change to help justify a new edition etc etc

 

[JohnD]

Might be something to do with the maximum reach of a tall person with long arms having one foot in the bath and one hand on the socket.

 

[Sneffels]

These diagrams are fantastic, thanks!

 

[flameport]

Wall mounted light switches have been permitted in bathrooms for ever. 600mm from the bath, or previously out of reach of someone standing in the bath, which is effectively the same thing.

Pull cords were never required for light switches in bathrooms.
They have always been an option - just as they are an option for use in any other room.