So what has actually happened here? Is this a member of LNwR staff who hasn’t been let on, or someone else (LU judging by the handle?).
Whilst I’m sure this sort of thing used to happen many years ago, there’s a number of reasons why it’s nowadays a no-no. What might have been better, assuming this was during disruption, is if they could have got control to make the service into a passenger working, however this in itself would require a few obstacles to be overcome not least availability of a guard.
Whilst carrying staff where possible is a good thing if it means a subsequent delay or cancellation is avoided, even if on another operator, there are times when it’s not possible. Especially if the reason the train is empty is because there is a defect of some kind, the presence of additional staff can be quite a distraction. The last thing one wants, for example, is a train where isolations have been made to safety equipment and there’s an off-duty member of staff there making a fuss that they need to pick their kids up from school or whatever - and believe me this scenario happens!
One way or other, not sure what the value was in sounding off on social media.