Is there not a duty on passenger to all that is reasonable & practical to ensure their tick is valid for travel.
That is a VERY good question, (although the way you phrase it suggests you already have a view!).
My quick answer is : No.
The ticket is the token which indicates that a transaction has been completed (the traveller paying a fare) and that the TOC has contracted themselves into an obligation to convey the ticket holder.
Any "checking" would rightly be carried out at the time of purchase; but at that point, we can only expect that would be to confirm that it requires the TOC(s) to convey the passenger at the time and to the place intended (and NOT to confirm that it entitles the traveller to be conveyed - it wouldn't be a railway ticket if it didn't!).
The long answer is : Yes, but only up to a point.
As above, the ticket acts as a token - it indicates that one element of the contract has been completed (the payment).
The question of checking that "it is valid" can have 2 meanings
- in most circumstances that would mean some confirmation that it wasn't a forged, stolen, used, ancient or otherwise improper to be used as confirmation that the Payment element of a contract has been completed
- the special meaning of 'valid' which is used on the UK railways is not the normal use of the word. This is a validity which has nothing to do with checking that the token (the ticket) is genuine and still available for use - its a meaning which includes additional prohibitions on use, some of which ONLY the railway operating companies introduce to tie passengers into some of their specific services (e.g. Specific timed departures or class of accomodation), and some of which are customer-related (e.g. being of the qualifying age for age-related discounts or being at the departure station in good time for a departure).
However, that second category (customer buying a ticket having correctly established THEIR eligibility for certain tickets) is surely something that can rightly be "verified" at any time between purchase and completion of travel, but, the first category, should not return the customer back to any position of doubt about the validity which was established at the time of purchase. (The transaction is completed - the Terms cannot alter).
The passenger still has some "reasonable & practical" obligations - to do with how they seek to take advantage of the right which the rail operator has granted to them (such as choosing to enter the class of accomodation corresponding to their ticket (their permit to be conveyed), but surely these must be restricted to the customer's obligations. Not to the rail companies' performance?)
To be clear about this - if the ticket is bought, in honesty, in good faith, and with full disclosure of all relevant factors, then it is NOT reasonable to
then expect the traveller to undertake further 'checks' on validity. They should feel entirely entitled to walk into a station bearing their ticket and board a train to their destination. *
Any 'checking' which results in restricting the passenger's right to be conveyed to their destination should NOT be introduced at the platform or on-board but, emphatically,
must be made clear at the time of purchase. And accepted by the passenger when taking their token which gives the TOC(s) a compulsion to convey a passenger (the ticket).
My assessment of the passenger's obligations to 'check their ticket' falters after the completion of their element of the contract (the payment). The remaining elements
must include the "performance" - which in the case of rail travel is remarkable, because it places an obligation on the railways to convey the passenger, but places absolutely no obligation on the passenger to travel.
[* Verring off topic, but consider: TOC provides half-hourly services from SmallCity via MidTown to BigCity. Passenger is on platform at MidTown ready to board the 12noon service to BigCity and holds a 'valid' ticket for that 12noon train. A train arrives just before noon from SmallCity to BigCity. Its the delayed 11:30. Passenger boards. Passenger is denied 'validity'. Passenger is accused of failing to check what that is "reasonable and practical"????]