Yesterday I had to travel from West Ruislip to Birmingham, although it’s a Tube station there is a Chiltern ticket machine at platform level which I decided to use because I had a problem using my chosen train app. However, some scrote decided to spit on the touch screen, so instead of using it I decided to buy a ticket from the guard, but I didn’t see one until past Banbury. He then refused to sell me a ticket saying I should’ve used the ticket machine wearing gloves! Anyway I eventually persuaded him to sell me a ticket, but who was in the wrong?
It's unsurprising you didn't see a guard until after Banbury, because 99% of Chiltern services south of there are Driver Only Operated - i.e. there's no guard scheduled to be onboard.
Unfortunately, whilst the fact that someone had spat on the TVM is disgusting and means that, in any circumstances but especially at the current time it isn't reasonable to expect you to use it, it's not quite that simple legally speaking. The reasonable and legal positions can sadly sometimes be somewhat removed from one another.
The only bit that is definitively nonsense is the suggestion that you should provide your own gloves to use the TVM - what on earth was the guard on about there?! Wallet, keys, phone, mask,
gloves? I don't think so! And even if you were expected to bring gloves, it's not like there are biohazard disposal facilities at stations. So that is a non-starter unless they want the spit wiped all over their bin lids...
In terms of avoiding liability to pay the undiscounted Anytime single fare under Condition 9 of the National Rail Conditions of Travel, you'd have to suggest that the TVM being covered in spit meant that:
there is no Ticket office open or self-service Ticket machine in working order
which I think is probably a viable argument given the circumstances. (Though, how did you pass through the barriers at West Ruislip in order to use the National Rail ticket machine on the paid side?)
In terms of avoiding liability for a Penalty Fare, you'd have to make the case that
there were no facilities in operation for the sale of a travel ticket for that passenger’s journey
which, whilst probably intending to mean the same as what the NRCoT say, has subtly different wording - c.f. working order vs in operation. I think it's a little harder to satisfy that the TVM wasn't "in operation" just because it was covered in spit. On the other hand, an argument that
there are compelling reasons why, in the particular circumstances of the case, the appellant should not be liable to pay the penalty fare
is much more likely to be successful, though it would appear that the intention is that only the appeals bodies can judge whether or not this ground of appeal is met, and not the County Court as would apply for a Penalty Fare that has fundamentally been issued in violation of the Regulations and their incumbent exceptions. That of course leaves you open to the vagaries and incompetence of the appeals bodies.
Finally, in terms of criminal liability, clearly you would lack the intention to avoid payment of the fate necessary to secure a conviction under section 5(3)(a) of the Regulation of Railways Act 1889. Luckily, we are back to the "working order" definition for the relevant exception to the otherwise strict liability Byelaw 18:
there were no facilities in working order for the issue or validation of any ticket at the time when, and the station where, he began his journey; or
which, as discussed above, likely exempts you from liability as a spit-covered TVM is hardly in working order.
Now, even if legally speaking it's arguable you could be issued with a Penalty Fare (albeit there may be other grounds of appeal
viz. defective signage), clearly from a customer service point of view Chiltern cannot possibly expect you to have used the TVM given the circumstances.
Accordingly I would raise a complaint with them, because the attitude demonstrated by the guard was utterly unacceptable. It also treats passengers who are clearly honest (who else would proactively seek out the guard, when they had no obligation to do so and knew there were no routine onboard checks in operation) as dishonest, which isn't on.
Don't expect to get anything remotely resembling a reasonable response, but - you miss all the shots you don't take!