Although Monument/Bank is now considered one station for gameplay purposes and should properly be played as "Monument/Bank", on boards up to at least 1987 it was shown as two stations, Monument and Bank (not going too fast for you am I?). The two were shown with an escalator link between them, usually represented as a zig-zag line. Consequently, under Chalk Farm '84
rules a move from Monument to Bank is legal, provided the player is not in spoon, and increases spin
and token loadings accordingly, but leaves LV unaltered. The fusion into one station means that, under later rulesets, if one player plays "Monument" or "Bank" rather than the combined name, his opponent may declare "Escalator" and then move as if at the other part of the combined station, eg to Green Park, with consequent advantages.
Similar maneouvres are, of course, possible at Tower Hill/Tower Gateway and Bow Road/Bow Church but these are more recent innovations, Monument/Bank is considered traditional.
This sort of frivolous anomaly is part of what makes the Game what it is.