In message , at
22:40:08 on Mon, 22 Oct 2012, Arthur Figgis
remarked:

Don't FCC have some complex restrictions on trains out
of KX if you happen to hold an off peak ticket?

Yes, but they will probably be time specific,

A very simple time-specific restriction.

rather than something else specific (though the option to go via
Liverpool Street potentially complicates things with the Cambridge -
London specifically).

The normal Off Peak Day Return has the same restriction from Liverpool
St. However, there's a Greater-Anglia-only off peak Travelcard which has
no evening blackout period.

--
Roland Perry