I remember the signal change, although I just missed the Hampstead - Golders Green single line working because I'd popped over to the Picc line for eleven months as a driver before moving back to the Northern.
The signal numbering sequence was strange.
Looking at an earlier diagram, the Edgware branch signalling was:
A124 (CT1 inner home), A125 Camden Town starter, A126, A1261, Camden Town NB starter was A1251, A126, A1261, then S128A and the numbering carried on upwards in even numbers (with a couple of odd numbers), until A154. A1541 was the last auto signal before the GG junction signal.
On the SB from GG tunnel mouth, the signal numbers carried on upwards in the same even sequence, starting with odd signal S157, then even numbers until A192A, which was the inner home at Camden Town SB.
It seems like they didn't like using odd numbers!
When the signalling was renewed from Camden, the NB numberiing then became:
Camden Town 1 starter A126, A128, A1281, A130
The numbering then increased, in even numbers, until A154, then A155, then the junction signal.
The SB numbering started at A157 (first signal from the tunnel mouth, then A158, A1581, followd by the F signals at Hampstead, then carried on in rising odd numbers from A167 until A189A, the outer home for CT2.
I know that over the years the line was signalled in sections as it was were built, and no doubt the signalling was renewed in sections, probably based on how long ago the last renewal was, but it seems strange that the numbering sequence wasn't standardised with the rest of the line - e.g., as a generalisation:
Starting from Morden going north along the NB, the highest signal number is at Morden and gets smaller, all numbers are even.
Starting from Morden going north along the SB, the highest signal number is at Morden and gets smaller. All numbers are odd.
This is the standard method of numbering throughout the rest of the line.
The Signal Reference Book centre supplement shows the numbering at a glance:
[ Click here ]Obviously, this is now all irrelevant as the original signalling system is now no more!