So I was in the England and touring palaces as you do and went into a royal chapel in which the Eucharist was reserved, along with a red lamp, a kneeler for worshipers and a sign urging tourists to show respect.
Although I treat all things regarded as sacred by others with respect (out of respect for the people) as an unbeliever of course what was present was exactly what was present in a Catholic Church.
Later I realised that for a Catholic this could create a quandary. Given the doubts over Anglican orders (at least those augment in the Old Catholic line) is was possible that this was, in the Catholic sense, validly consecrated reserved communion bread. It was also possible it was not, should the intention of one of those in the apostolic succession behind the priest who consecrated the communion bread be invalid.
So what would a Catholic do? Simply walk past and ignore what was there? Or worship? The one would seem to be to be at least a minor sacrilege and the other at least potentially idolatry.