Is belly button poking so common is England?

Literally I was at campsite Spain, Had a good time with a English couple ( we are also couple visiting from Italy ).

My God that Man let's call him Lui and woman Sara

For the whole camp site evening. He was continuously digging Sara's belly button, licking her, poking her.

For at least 10-15 minutes, lui's finger was embedded in sara's navel, literally in, he was wiggling poking etc not letting go

Surprisingly he did tell me about navel fetish in England being popular.

How true is that ?