ONGAR STARTING SIGNAL

I don't have any definite information but would assume that control of the starter at Ongar would be achieved by effectively making it controlled by the signal relay that previously controlled the advanced starter (LZ29). This would have the effect of placing on the starter the controls previously effected upon the advance starer by the signal boxes at North Weald and Epping i.e. even before Ongar signal box closed the advance starter could not be cleared unless the signalman at North Weald (or Epping if North Weald was switched out) accepted the train onto the single line by operation of a permission lever. With the closure of Ongar Signal Box these permission levers would become the sole control on the starter at Ongar and thus if North Weald was open then it controlled the signal but if North Weald was switched out then Epping controlled the starter under the pre-existing arrangements for switching out North Weald. Doing it this way would minimise the alterations required to the signalling at North Weald and Epping consequent upon the closure of Ongar and indeed the subsequent closure of North Weald in 1976 would probably have been handled in similar fashion by making the remaining signalling believe that North Weald Signal Box was in the 'switched out' state, thus handing full control of the single line to Epping.
This is all speculation on my part but it is not dissimilar to the way the Chesham branch was treated in 1970 when the signal box there closed. In that case the starter and advanced starter at Chesham had been slotted by No.69 lever in Chalfont IMR and when Chesham Signal Box closed the starter and advanced starter became controlled solely by this slot lever and they were thus re-numbered JT69^A & JT69^B respectively.

When I get the chance (probably not until the New Year) I shall speak to a colleague who was a relief signalman on the Central in the 1970s and who remembers working at North Weald.

As a corollorary to Harsig; the following from the opening peril 42/1957 which covers the electrification to Ongar may well be germane, given that there is plenty of photographic evidence that North Weald was switched out after the last crossing and the levers were left exactly as needed for when North Weald switched out - but of course the track was lifted and the points plain lined! The video 125 DVD of the Central Line has some good interior shots of North Weald box in this 'permanently switched out' state - note this is not the same as 'closed' [1]. I'm fairly sure that the diagram was altered to just show track circuit occupation on the remaining single line.

When North Weald signal box has been closed and the automatic working lever no 11 has been reversed, the single line between Epping and Ongar will work as one section, and will be controlled by the Epping Signalman. In these circumstances signals LW.21 [2] or LW.22 [3] and LW.20 [4] at Epping will not be lowered until levers no 3 [5] and either nos 4, 8, and 9 [6] have been reversed and all track circuits between Epping and Ongar are clear. Similarly signals LZ.29 and LZ.30 [7] at Ongar will not be lowered until all track circuits between Ongar and Epping are clear, and the Epping Signalman has reversed lever no 1 [8] to give permission for the train to enter the single line.

It is salient to note that prior to this iteration of the signalling, there was a detonator placer in the branch, worked by lever 19. This was presumably a belt-and-braces protection method for the steam trains approaching Epping, due to the differing braking distances and coupling heights.

[1] prototype example (so the story goes) - Rhiw Goch on the Festiniog, it was switched out for almost 15 years, the signal heads even made it down the valley to Boston Lodge - but when the 'box reopened all that was needed was for the heads to be recommissioned and the wiring checked over. There wasn't a need for a formal reinspection because the 'box had never actually been decommissioned.

[2] LW.21 - starter from No 1 platform at Epping to Ongar

[3] LW.22 - starter from No 2 platform at Epping to Ongar (via 10 crossover reverse)

[4] LW.20 - Advanced starter on the Ongar branch

[5] Ongar 3 - Outer Home

[6] Ongar 4, 8, and 9 - Inner Home and selected subsidiary disc

[7] LZ.29 and LZ.30 - Advanced Starter and Platform Starter at Ongar. (LZ.30 was about a third of the way down the platform)

SO; how does this relate to the original question? Well, the circuitry was in place to allow limited (ie. not 'free') acceptance from Epping to Ongar. Applying Occam's Razor, the reversal of lever 11 at North Weald united the acceptance conditions of both short sections, this still applied when North Weald loop had been lifted, so the answer to your question is:

From 1969 until 1976 Ongar Advanced Starting signal LZ.29 (eventually the only WB signal at Ongar) was controlled by lever 21 at North Weald when North Weald open (and lever 11 normal).

From 1976 until closure, LZ.29 was controlled by Lever 1 at Epping with the condition of Lever 11 being reversed at the partially decommissioned North Weald.

As Harsig quite rightly suggests, lever 1 at Epping was a slot lever - after 1976, the slot would have worked directly with LZ.29 at Ongar, but the circuitry was still in place at North Weald and Ongar to check the state of the track circuit occupancy; the slot before 1976 would have been lever 21 at North Weald.

Really, if the rules applying to signal identification had been applied with maximum pedantry, LZ.29 should have been plated XLX.21 or XLW.1.

I've done a bit more digging and LZ.30 did indeed become LX.21 when Ongar signal box closed.

EDIT: Just to clarify: LZ.30 (the starter at Ongar, a third of the way down the platform) was the only westbound signal remaining - LZ.29 (Ongar advanced starter) was removed when the 'box closed.

the hanging footnote [8] was meant to refer to a note about slotting and working directly with the signal - IOW the controls at Ongar had been removed, the switching was done by Epping or North Weald as appropriate.