Lots of good stuff here - many thanks for the interest and comments.
Just on the question of operation sequences ("pull lists"), familiarity and experience is key, but rest assured that the Relief Men in busy areas with lots of large boxes all carried a "little black book" which would see much use during the first few hours in a box which they had not worked for several months!
Pull lists can be lengthy - there are several at Exeter West (131 levers) which are 15 or more levers - but the frame is well laid out, so most of these start "32 then all the black ones to 54..." Hope you will all call in to the Crewe Heritage Centre to see how it is done!! And of course, download my Simulation from the link in my signature!
In the case of Leeds City junction, there are no really difficult pull lists - most are only three or four levers and none longer than 7 BUT there are (including shunts) no less than 28 different possible routes! And up to 6 of them can be in use at the same time - here is a view with 6 routes all in use at the same time :-
pulled off 2.jpg
You can see (by the white stripes) that there are four Section Signals reversed - one of these is a block-controlled shunt signal. (there is actually a fifth Section Signal, but it is "slot", rather than "Block" controlled. Also the block of levers from 48-55 all reversed apply to three different routes! We are currently working this layout with switches and I can assure everyone that getting confused is not difficult! In this example, you would have three trains, two light engines and one shunt into forward section all on the go at the same time.
Terry is right to mention two or more men manning a box - and in this case, the frame is laid out for two men, and the division is marked by a spare lever in the middle of the frame (the other spares result from installing colour lights and eliminating Distants). Of course, two men doubles the risk of confusion! And the booking lad may or may not help...
Here is one for the signalling enthusiasts:-
distants.jpg
Two Sop signals, but THREE Distants?
The question of what value all this adds to a model railway is personal and dependent on circumstances, so I am sure Martin will have no problems at all at Burford [many thanks for the kind words in Snooze 207 Martin - they are well received] but equally, I know he is just dying to get his hands on those nice shiny etches!
But other layouts have other problems - I am fortunate to have visited on several occasions, a very well known and large model of a station on the ECML and the highlight is when the A4 Pacifics "streak" through at the head of 10 coach rakes. There are three large signal boxes, and the levers frames are represented by banks of switches - impressive: but no locking! This raises the hazard of said A4, running full speed under clear signals straight into a dead end bay!!! Luckily it is not DCC with "inertia"!
Of course, the signalmen are alive to such a risk, and armed with their written-out "pull lists" they set the road VERY carefully! BUT here is the rub! The consequence of this is that only one move ever happens at a time and it takes several minutes for the road to be set then cleared with the result that for most of the time absolutely nothing happens!
And here lies another important point which might get overlooked - you can get 80% of the benefits of locking from only 20% of the locks. In the case I describe, just interlocking the points and running signals would give the signalmen and drivers confidence that if the signal is Off, then the road is set. This would have a massive operational benefit in terms of speeding the job up. So, such things as Shunting Signals, let alone Conditional Locks, Flank Protection, Hold the Road, Sequential Locks, etc are fine for people like me who enjoy this nonsense, but mean a lot of work for little gain for others. That said, I am not volunteering to build the frames for that layout - I am sure an electronic solution will be much more practical!!!
In the Case of Minories, we operate a very intensive service and the locking gives us confidence that we have done it right and allows very quick working with out (too many) mistakes. Remember that FormerEditorJames is in the crew, and given all he has said about Good Quality Operation, mistakes cannot be countenanced! But there is a more important factor in our case, and that is that we want to show the public a little bit of what a Signal Box is all about - albeit that some of them will not be interested. Tim V's Clutton showed the way in this - though other did go before. When we exhibited at Warley, was great, from the back of the layout, to observe the eyes of the viewing public - they would follow the train in and as it came to a halt, all eyes would turn to the signalman, and as the levers stopped moving, they would all turn back to the next train ready for it to move - that made it all seem worthwhile! And it gives people something to watch when the trains are not moving.
Best wishes,