O.S. Nock's excellent book 'Electric Euston to Glasgow' (Ian Allan, 1974) has a very detailed chapter on the Weaver Junction-Glasgow resignalling, with full track and signalling diagrams for the four new power boxes at Warrington, Preston, Carlisle and Motherwell....plus the new panel installed at that time in the 1961-vintage Glasgow Central power box. Of great interest is the fact the diagrams clearly show the currently-existing box at Carnforth Station Junction (the junction for Skipton) and the now-closed (1997) box at Furness & Midland Junction as having been abolished, with two aspect alternating distant and stop signals between there and Arnside....with the latter being the fringe box to Preston. I can only assume that this part of the scheme was cancelled at very short notice....probably due to lack of funds. Or was it deemed necessary at the time to retain the Furness & Midland Jn to Carnforth East Jn avoiding line as a strategic diversionary route for nuclear traffic to and from Sellafield? - the reason why, as several old hand Skipton drivers told me, Carnforth to Settle Jn was never singled. Photo plate 16 in the same book clearly shows the ex-LNWR Carnforth (Middle?) Junction signalbox on the Up side of the main line at the South end of the station....and I believe that there was another box about three quarters of a mile further South at Carnforth South Junction.
I've read that the reason for the slightly odd situation at Carnforth Station box, and the discrepency with the signalling diagram printed in O.S. Nock's book is this:
In the late 1960s, at the time BR developed its Business Case for the Treasury to approve funds for the Weaver Junction - Glasgow electrification, the "hot button" to press for a favourable ministerial signature was to include a statement like "this investment will allow us to close and dismantle XX miles of track on other route(s)".
In this particular scheme, the stated plan was to close the Settle & Carlisle, the Blackburn - Hellifield and the Carnforth - Settle Jn lines as through routes on completion of the WCML electrification.
Single-track, freight-only branches with minimal signalling & maintenance requirements would remain for occasional quarry trains between Skipton & Horton-in-Ribblesdale, Blackburn & Horrocksford (Clitheroe) and from the Carlisle end (to Long Meg?)
The Carnforth - Settle Jn line was to disappear completely - hence preparation of plans for Preston PSB to control the Furness line as far as Arnside which are shown in Nock's book.
It also explains why TCB resignalling of the East Lancs Line through Blackburn under the new Preston PSB did not include any of the line towards Clitheroe & Hellifield, nor did Carlisle PSB control any significant length of the S&C at its northern end.
As it turned out the lines had a reprieve for long enough for the original closure threat to recede.
The
Electric Euston to Glasgow book is certainly a good account of the northern WCML electrification project with much useful and fascinating detail. But I always get the impression the book was published in a desperate rush to coincide with the start of electric services.
A number of errors did make it into print (like the Carnforth - Arnside signal diagram) which I charitably put down to publisher & printer time pressure, rather than lack of diligence on the part of Nock. However, the final signal notice for the Carnforth station area was published to BR operations staff in November 1972, which should have been enough time for the correct version to get into the 1974 book.
Ian Allan and Nock might have done better to publish the book a year or so
after the start of 'Electric Scots', included a final chapter about the actual service implementation and fixed some of the errors (and found a better-quality photo of an electrically hauled train running north of Weaver Jn than the one used on the dust jacket)
The Signalling Record Society have made the 'Preston Signal Box Stages 3, 4, 5 and 6' Special Notice 1203G available for download on their website. It's an 8.9MB file, but those show the 'as built' signalling at Carnforth during the 1972-73 period:-
https://www.s-r-s.org.uk/pullfree.asp?FilePath=ArchiveSignals\Downloads\brmr&FileName=1972-1203g.pdf
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