Hello
On strike days it's usually possibly to travel from Cambridge to Ipswich, albeit just not by a permitted route.
Are there any options for arguing the second bit of a Cambridge - Ipswich open return can be used? Or do I need to suck it up and pay £


?
In theory, if you bought your ticket before the impact of the strike was apparent (e.g. before it was announced, or before any warning was shown), you would be entitled to be re-routed that way; the delay by waiting for the next direct train would be into the double digits of hours and thus you can exercise your right to re-routing under
Article 16 of the PRO.
In practice, whilst on the one hand you may be lucky enough to come across a member of customer service staff (as reported in
this thread) who is very helpful and willing to endorse your ticket, and any contingency guard on the London to Ipswich train is unlikely to check tickets, I would expect gateline staff (e.g. at Liverpool Street) to be difficult as they are usually given little or no training on these sorts of issues.
I would ask Greater Anglia to re-route you (if you are told "we can't" or "it's not our problem", try a few different people/methods to see if you get another answer). If they refuse, get that refusal in writing and then you will have the evidence you need when you contact them to claim back the cost of buying tickets for the alternative route.