"D7666" wrote in message
...

Actually one of the *ultimate* signalling difficulties - if not the UK
all time ultimate difficulty - would occur about 1 km to the west of
London Bridge where it is possible to grid lock Borough Market
Junction triangle with three 12car trains in the wrong place ... the
layout is such that the rear of each one of the three trains obstructs
the route of another ... and it is not just the route is locked but
track unoccupied, it is the rear of the train is literally on the
tracks in front of another.

No longer possible. There is no pointwork at Borough Market Junction any
more - London Bridge platforms 4, 5, and 6 and the Up Passenger Loop only
lead to/from Metropolitan Junction (thence Charing Cross or Blackfriars)
while platforms 1, 2, and 3 only lead to Cannon Street.

Peter