In message , at 09:19:35 on
Sat, 26 Jan 2013, Brian Watson remarked:
I found myself thinking, "why start at Shenfield?"

Is there so much demand on that line for such a route, or capacity further
up it (at Chelmsford for example)?

Shenfield is where the line stops being 4-track and splits into two
2-track lines (one to Southend the other to Chelmsford and beyond). As
well as being a junction, it's always been an important railhead and
interchange point. And the "town on the edge of London" although being a
couple of miles inside Essex.

Also the railway through Chelmsford, and the station itself, is on a
brick viaduct, which makes any additional trackwork required to turn
back a large number of trains somewhat impractical.
--
Roland Perry