I mentioned this is another thread and said that I would dig out the old cable code which was used in the U.K. in years gone by.

So for anyone interested in long-obsolete systems from an ocean away, here are two pages which describe the coding and cable makeup from Atkinson's "Telephony," 1950 edition:

https://myweb.tiscali.co.uk/paulcoxwell/TEL/Tel1_295.jpg

https://myweb.tiscali.co.uk/paulcoxwell/TEL/Tel1_296.jpg

It's not shown in the chart, but the standard 4-wire cable used for subscriber premises wiring used the solid colors blue, orange, green, brown.

That's as bad as odd count pic. Thanks for sharing.

What is the 3rd wire used for on the British system?

Nope, don't push your site or supplies.

My apologies for missing this question over a month ago!

The cables listed as "triples" on those pages were typically used for internal exchange wiring. The third wire of the circuit was for control -- The sleeve connection on a cordboard jackfield or the P-wire on Strowger switches (used to mark busy trunks and control the holding of the connection).