Yes, if they enquire, but if not, there is no reason for the clerk to do so, they would be making work for themselves and I don't believe you can truthfully say that is a railway only issue.
Yes I agree,
if they said something like "can I avoid London to avoid this problem?"
then the split should be offered (or the ticket from Chichester) IMO.
But that analogy is flawed, if the customer returns the item and the next size up was £5 more, would they be expected to pay the £5 to get the bigger size or be let off because it was just an error of judgement. Would the shop be fined for selling the wrong size? I also believe that if it is not 'faulty' the shop doesn't have to give a refund or a replacement, but may do so as a goodwill guesture.
The equivalent analogy would be if a shoe was advertised as a size 6, and a size 7 was advertised as £5 more, if the customer discovered that someone in the shop had labelled the sizes one size too small, so the size 6 was actually a size 5, and brought it back, it would be reasonable to expect a replacement at no additional cost. In other words, if the customer was told it was the size they require, but this was an error by an employee at the store with labelling, the store would be liable.
In our situation the customer would be sold the excess to the correct price for the time of travel, therefore paying no more than they should have anyway.
But the key thing is if they are told by an employee that they can do something at a certain price, that should be binding.
Bearing in mind most tickets can be sold from any part of the country, a conductor can't be expected to have the correct phone number for every ticket office in the country.
That's an internal railway matter

I agree, but perhaps Control should, but that's not the customers' concern.
IIRC the railways internal phone switchboard didn't even have numbers listed for some Virgin run Booking offices for a while a few years ago because they had been changed.
Again, an internal railway matter.
It also implies clerks work 24 hours a day, which they don't of course, or even that the office in question is even open when they need to be contacted. They could write 'validity advised' on the ticket, but then how do we know the right ticket validity was given? Perhaps we should write the entire conditions on the ticket, just in case! (no, I'm not being serious)
Well I doubt the entire conditions would fit, but someone said in another thread that the code could be printed on the ticket, and yes it should. Restrictions should be given with the ticket - this requirement exists but isn't essential, it doesn't say "must" but "should", hence it is very rarely done.
And you have reliable proof that it is a problem (widespread or otherwise) caused by lack of staff training and/or knowledge?
I give you this
evidence supplied by kwvr45, a guard I've not (yet?) met kwvr45 but I know he is genuine and know people who know who he is

so yes, I believe it to be true.
Certainly the railway should do it's best to make sure the correct fares are sold based on information about the journey being made, but that won't elliminate the problem because people make mistakes, no-one is perfect afterall.
I understand that. But any shop that looks after it's customers, would honour a deal offered by an employee that makes a mistake, and I don't see why the railways should be any different. Until money changes hand, the deal doesn't have to be honoured, but most shops would honour it anyway. But the key thing is what happens when money changes hands,
a contract is then made. At this point, both parties should be expected to honour the contract. If the customer is told of a condition and travels at a barred time then they will be asked for an excess fare, but if the customer is told they can travel at that time and it was a mistake by the employee, the railways are liable and to charge the customer extra the railways would be in breach of the contract.
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I think what confuses the public most are the restrictions when you travel on two trains.
I'm not sure that any such restrictions actually exist?
If perchance there was a through train from Havant to Leicester, then leaving at 14:45 in the afternoon is clearly off peak.
Actually no, if there was a train that went through the Thameslink tunnels, it would be barred throughout as the customer would be travelling on a train that departs from St Pancras at a barred time.
But because he has to change, all of a sudden the departure time of the second train changes the rules as he has to know if that train is peak or off-peak. To the public that is plain bizarre.
Not true, as if this was true, the customer could avoid the restrictions by going via East Croydon, changing there for a Thameslink service to Bedford and then changing to EMT. This would not be valid as both the Thameslink and EMT trains are barred on the basis that the
trains departed St Pancras at the barred time, irrespective of the fact the customer did not board at St Pancras.
If the restriction said that the
customer could not board a train at
St Pancras at certain times,
then I'd agree with you.