I have been in one. Just not recently and not in that way. Long before the channel tunnel, refugee crisis (plural) or camps, I sought out an asylum. In Saint-Remy-de-Provence, France.
That’s where Dutch artist Vincent Van Gogh voluntarily admitted himself during the last year of his 37.
A locked facility for the mentally ill, he had travelled to the asylum from a hospital in Arles, the subject of one of his paintings:

Hospital garden, Arles
Crowned by French locals as ‘Fou Roux’ (the red-headed madman) Van Gogh produced painting after painting birthed from a place of extraordinary mental anguish and physical difficulties.
I went to the hospital in Arles too for a day. Looking back it was probably not everyone’s idea of a traditional happy-go-lucky holiday itinerary.
But my pilgrimage did confirm that the busy galleried hospital walkways of Van Gogh’s painting are still populated by madmen and asylum seekers.