wrote in message
oups.com...
I noticed at Brent Cross the other day that a section of conductor rail
about 20 feet long had been welded in. Seemed odd that a short section
of conductor needed changing, now track I can understand.

Could it have been badly burned by excessive arcing between rail and shoe?
If it had been at a point where many trains suddenly applied power (eg as
the train was starting from station or signal) it could have become so
pitted that it caused further arcing through poor contact - cue vicious
circle!