Main line Railway Station - London 1944

[Segilla]

A train from London to Braintree Essex would have left from Euston or St Pancras?
LNER?

[dzug2]

It would have left from Liverpool Street - LNER as you say. In those days I'd guess that a change at Witham might have been needed

The station was called Braintree and Bocking originally - don't know when the Bocking was dropped.

[Fitzer]

Braintree used to be served by two branch lines, one from Witham and the other from Bishop's Stortford, both of these were fed from Liverpool St. So neither of your two seems likely.