Clive D. W. Feather wrote:

On LU, I am not aware of any specific rules.

So, following your rules as posted, a 165 approaching Moor Park NB with
a Met in front would see this:

3 3 4 4 4 4 4 4
A858 A860 A864 A866 A868 A870 JJ48 JP47
|-O |-O |-O |-O |-O |-O |-O |-O

R A60
Y R A60
G Y R A60
G G Y R A60
G G (!) YY Y R A60
G G G YY Y R A60
G G G G YY Y R A60
Moor Park

Note that a green 3-aspect signal (A860) can be followed by a double
yellow 4 aspect signal OR a single yellow 4 aspect signal (A864) - if
I've read your post correctly, on NR this is a Very Bad Thing.

Unless A860 is held to yellow if A864 is single yellow? Or have I
managed to misunderstand?

snip/

Does the yellow aspect still have the big black F burned into the
lens?

I believe so.

Thanks.