It is difficult to imagine a situation where one of the members of the royal family used regular public transport. Usually it is intended for ordinary people. However, sometimes even monarchs can ride the subway or bus. True, exclusively for work.
Just a piece of work
Naturally, it is easy to assume that the queen will not stand in line for a bus or buy train tickets. And you also have no chance of accidentally seeing her on the subway while visiting London.
Members of the royal family move in special vehicles, accompanied by bodyguards. Inside, usually “dummies, ” not ordinary passengers. There is nothing surprising in this: basic precautions.