and has to be slightly aggressive to get his job done.
No he doesn't have to be agressive at all.
Agression dosen't solve problems. What is needed is a change to railway ticketing systems. They will have to accept that its not always the fault of the passenger if they have missed a connection due to another train or service running late.
Lets take a typical railway or most any transport system.
There will be peak times when everyone needs to get to work in the morning and the evening so the trains busses coaches roads whatever will be well loaded. The rest of the day they will be running but mostly empty as there isn't the same level of demand outside peak times.
So in order to drive revenue and to make money they will offer cheaper off peak fares to entice people to use public transport services. All well and good.
However the real problem is/seems to be selling tickets for a particular TIMED service. Now the OP states;
But of course the train was stuck at a red light for 10/15 mins and the tubes were awfully slow.
So she relied on the rest of the rail system which in this instance let her down. Now our "grip" (railway slang for a ticket collecter inspector as he "grips" your ticket) sees that shes on a later service as she was delayed by another part of the rail system.
Now whos fault is that hers or theirs?
Now the grip could accept her reasons and an experenced one usually knows where there is a gen problem or someone is swinging the lead. And its up to the railway to promote its own use and it can been seen here where the grip has acted more reasonably its left a good impression and people will use them again. As can been seen by the OP comments "screw the public transport service I'll take my car."
I think the best way of solvinig this issue is to do away with timed train services, so you use any service after say 09:00 Hrs up to say any before 17:00 then after that say 19:00 hrs onwards.
So thats a simple ticket system and anyone using a service outside those hours for any reason will then have to pay a surchage.
And that to be made plain on the ticket too!
Far less room to have run in's with the poor old grip whos only doing his/her job after all:)