I think Portillo is a Latin word meaning Pompous A s s. (printed like this, since the alternative name for a donkey is considered indecent on RP)Agree VG on the pomposity but at least there is usually so little rail component, much of which is contrived simply to link the places he visits, it doesn't matter from the rail perspective. At least there are no artificial 'massive, catastrophic, disasterous' incidents of track faults, brake failures etc etc included which just make the people and the industry look incompetent and stupid.
As for the donkey bit that is just childish.