Elephant and Castle - 1941

1's was a free lever and had no stick relay. I wasn't aware it had an A sign though.

As an aside, BR3, the SB starter at Lambeth North, does (though there is no circuitry for it).

What makes signalling so interesting is its uniqueness. There are many standards but many more exceptions. As we always used to say, if one instance exists then it is a standard!

I worked all over the combine and site prints for many disciplines were out of date or missing. I also know that the drawings offices routinely microfilmed office copies and then binned the originals to save space, subsequently mislaying the copies but I never came acoss a case of a missing bookwiring except when it had been purloined by the local AET. This was the practice at some depots adjacent to IMRs.

Of course mistakes and anomalies do occur from time to time, but we used to pick those up on wire counts, and some were discovered in the first tranche of IRSE Licensing tests as well.

i think harrow is still push pull i cannot confirm this as i never been there just heard the horror storys from old locking fitters and aet's

Still is, but if I've understood my signalling design history correctly, there are substantial technical differences between the push-pull frames at Elephant and Harrow. The early push-pull frames, such as Elephant or Rayners Lane, interfaced directly with the signalling in the local area, the only other levers provided were point levers which, during normal operation, were left in the mid- stroke position and locked there by a control lever.
Later push-pull frames such as those found at Harrow or on the Central Line were arranged such that the route levers merely controlled levers in a remote air operated frame and thus were not directly interfaced with the signalling.

Regulation G5 (f) of Appendix 4 to the Rule Book 'General Signalling Regulations 1984' gives a description of the operation of the earlier form of push pull frame:

G5. (f)
(i) Route-lever locking frames are generally provided with a control lever which must be in the "pull" position for route signalling to be put into operation, and must be in the "push" position to permit independent operation of the levers controlling points. To enable any points to be operated by means of individual levers, all route-levers must be placed in their normal ("mid") positions, the control lever must be placed in the "mid" position and all point levers must be placed in positions corresponding to their indications.* The control lever must be placed in the full "push" position.
(ii) While independent point levers are in use, it is not possible for any signal to be cleared, and trains must therefore be hand-signalled in accordance with the relevant Rules and Regualtions.
(iii) In order to permit the resumption of route-lever operation of signalling, the control lever must be placed in the "mid" position, point levers must be placed in their "mid" position and the control lever must then be fully reversed to the "pull" position.
(iv) All trains within the area controlled from the signal box must be at a standstill before any change is madefrom route-lever operation to individual control or vice-versa, and where more than one control lever is provided the procedure described in sub-clauses (i), (ii) and (iii) above must be carried out for each section of the area controlled.

* G5 (e) (iii) says: If a pair of points or a crossover is reversed by the operation of a route-lever, the points or crossover may remain reversed even after the route-lever is replaced to the normal position. In this event, they will be replaced to normal only by the selection of a conflicting route.

Also note G5 (e) (iv) says: Special instructions concerning the operation of route-levers are in force at certain locations and the provisions of this Regulation may not apply at these locations.

I'm certain this last is a reference to the later push-pull frames such as Harrow as the operation of the frame there is nothing like that described above.

Yep, It's a few years since I was last in Harrow Cabin so I didn't know if it was still push pull or not. I do recall the slave frame though and watching the levers throw when the signalman was at the other end of the frame selecting routes.
AIUI the points are all operated by WRs and they remain where they lay until a newly selected route either throws them or not and then locks them.

Added.

Most of the horror stories I heard about Harrow seemed to be to do with the moveable angles!

Bookwiring masters are never microfilmed - they will always be a paper master. A lot of other stuff is filmed though.

'B', 'K' or 'N' - all to do with the reverse indication lock.

The only difference between Heffalump and 'arrer is where the mechanical cross-locking is located: front or back. [1]

There are more technical differences with the circuits - cold proving, contact bands made through differing degrees but very little difference with the 'frames - hence 'technical' - I suppose.

[1] I'm not sure at this point in time.