On 31 Dec, 21:40, Hertsman wrote:
On 31 Dec, 21:22, Peter Lawrence wrote:

I noticed yesterday, approaching S.P.I.L.L. from the north, that we were
one of two trains running side by side through the tunnel into the
station. *(All trains were terminating there.) * Can anyone explain how
this can happen?

From the Thamelink Programme website:

Signalling: The route across central London changes entirely. In 2011
there will be new crossovers to give First Capital Connect the
flexibility of running trains into either of the two Thameslink
platforms at St Pancras International, regardless of their direction
of travel. Could be this is now available for use!

From December 2011, signals will be installed closer together than at
present, like a metro system instead of approximately every 1km which
will allow trains to safely travel closer together, increasing
capacity.

From Easter 2012 there will be bi-directional signalling across the
entire core – from Kentish Town to Blackfriars and the bay platforms
at Blackfriars will be brought into use.

It has to be that the bi-directional signalling is in place. It can be
disconcerting to see it in operation, though. I remember when it was
first implemented south of Guildford, whereby southbound trains can
set off together through the tunnels, and it seemed most odd. For some
reason there, though, bi-directional running is only in the south-
bound direction. (I hesitate to use the conventional railway terms of
up and down because at Guildford, a southbound Portsmouth train is a
down train whilst a southbound Gatwick train is an up one.)