Inconsistent application of rules for using the pool at Bryanston Gym near Grosvenor

I use the children's pool at Bryanston near Grosvenor square on Saturdays. The rule for using it is that you should wear a swimming cap. My son has been picked out by a manager on one occasion. A week or so ago he walked through with other people not wearing a cap while we are following the rules and said nothing. He is a white guy with a tattoo on his left calf. This is really irritating when my son wants to swim without a cap but I told him those are the rules. It happens often that there are many people not complying and managers have walked through. Have the rules changed?