Edit: The more I look at this, the less sure I am that it can be reasonably stated that there is definitely no obligation to look for a conductor.
But isn’t this black and white now. I was asked to produce a ticket upon boarding the train, and I didn’t have 1. I didn’t locate or speak to the conductor to buy a ticket. In court that would be the facts and the rest is just conjecture.
The facts include what train companies have agreed.
National Rail Conditions of Travel said:
The key responsibilities of Train Companies...are:
...We...will ensure that you are treated fairly if you are unable to purchase a Ticket because advertised facilities are unavailable.
http://www.nationalrail.co.uk/National Rail Conditions of Travel.pdf
You might tell them,
"I believe that the law allows me to board ticketless when the office is closed and the machine doesn't work, because it's stated in the Conditions of Travel."
National Rail Conditions of Travel said:
6.1. You must have a valid Ticket to travel before you board a train where there was the
opportunity to buy one unless one of the following circumstances applies:
6.1.1. At the station where you start your journey, there is no means of purchasing a
Ticket, either because there is no Ticket office open or self-service Ticket
machine in working order; and where notices indicate that you are in a
Penalty Fares area you purchase a Permit to Travel if there is a working Permit
to Travel issuing machine...
You might also tell them,
"I don't know of any clear written requirement for me to look for a conductor in these circumstances. Nor do I know of any requirement to "pay the fare due on boarding any train immediately", as Transport Investigations Limited claim."
The conjecture is the idea that you were obliged to be inconvenienced by not just the broken machine but also by having to find the conductor.
Transport Investigations Limited said:
"it is always the responsibility of the passenger to declare the journey to on train staff and pay the fare due on boarding any train immediately"
Here again, you can quote the conditions.
National Rail Conditions of Travel said:
In these cases, you must, as soon as you are reasonably able, buy an appropriate Ticket to complete your journey.
That doesn't clearly say that "reasonably able" means you have to look for a conductor.
Then there's an information box, which is not part of the official conditions.
National Rail Conditions of Travel Information Box said:
INFORMATION: This means that you should buy a ticket from the conductor
on the train if there is one available; at an interchange station provided there is
sufficient time before your connecting service; or, if neither of these is possible,
at your destination.
At this point you can quote the part about "fairly" above. They say they will *ensure* that you are treated fairly. That would seem to mean that if in doubt they have to err on the side of leniency.
As posted above, TiL themselves say the ticket-checking staff "are notified" when the machines don't work.
So if I understand right, the only wrong things that have happened in this case may be nothing do do with you doing anything wrong, but that you have been inconvenienced by:
1) the company not providing facilities to buy,
2) the inspector wrongly refusing to sell you a ticket (after they were apparently not told the machine was broken despite the public information saying they would be told),
3) TiL pursuing you and
4) you being told on a perhaps shaky basis that there had been an obligation for you to find the conductor.
Transport Investigations Limited said:
What if I could not get a ticket ...because...the machine was not working?
...The train operating companies monitor these facilities, and where there are failures, the ticket-checking staff are notified.
http://transportinvestigations.co.uk/payments/have-you-been-reported/frequently-asked-questions/
People have different confidence levels about how they'd come across in court, and courts might be viewed as not tough enough on train companies.
But the company is supposed to be able to prove beyond reasonable doubt that the machine was working and/or that you were obliged to find the conductor.