On Jan 27, 11:14 pm, Steve M wrote:
Yes, that seems correct if reversing northbound to southbound. But the
original poster was asking about (or referring to) southbound to
northbound reversals, which would use said crossover after leaving
Euston SB and then run into the King's Cross loop to reverse.

The OP was describing a journey _from_ Euston _to_ London Bridge,
which means that he would have been on the s/b City Branch platform,
which means that his description is ambiguous - the two terminators
shown could have come from either KX or Camden. Since his description
did not define it, and since a south-to-north reversal is somewhat
more painful due to the need to tip out, I assumed that he was
describing a north-to-south reversal.

I've seen trains do this on the internal systems at work, but not in practice. I
don't know how often NB to SB trains make the move you describe above,
but it'd be useful in times of service disruption, or a suspension
around Camden Town.

Before the 1960s n/b diversion Euston was a regular, timetabled
terminus for Northern Line services, which made use of the scissors
crossover that was provided for that purpose. These days I suspect
terminators at Euston are much more rare, albeit easier to handle when
doing north-to-south terminations, thanks to the wide platform.