The conditions of carriage state:
"If you travel in a train:
(a) without a ticket; or
(b) the circumstances described in any of Conditions 10, 11, 12, 18, 19, 22,
30, 35 and 39 apply;
you will be liable to pay the full single fare or full return fare or, if appropriate, a Penalty
Fare (see Condition 4) for your journey. You will not be entitled to any discounts or special
terms unless either:
(i) at the station where you started your journey:
there was no ticket
office or no ticket
office was open
and
there were no
self- service ticket
machines or no
self-service ticket
machines were in
full working order
and
in Penalty Fares areas
you bought a Permit
to Travel unless no
Permit to Travel issuing
machine was in full
working order
or
(ii) the notices and other publications issued by the Train Company in whose
train you are travelling indicate that you can buy tickets in that train.
In circumstances where (i) or (ii) apply, you only need to pay the fare that you would have
paid if you had bought a ticket immediately before your journey.
Now, in your case, boarding at Rugeley Town, you are in a penalty fare area so assuming the permit to travel maching is working you must purchase a permit to travel, else a TTI will able to charge you a £20 penalty fare or the guard will be able to charge you the full, undiscounted, fare for your journey along with a penalty fare warning.
This of course assumes that there is no notice which states that you may board the train without a PTT.