M&S Angel Islington - This store targets black customers for security surveillance

Yesterday I went into my local M&S in the Angel, Islington. My partner and I were followed around the store from the moment I picked up the loaf of bread that I had gone into the store to purchase, until I paid for it at the self-scan checkouts. Highly frustrated, as I left the store, I asked the security guard who he was going to follow next. He replied "no-one". I snapped back that that was because he only followed black customers. He answered back, "yes". Shocked and upset, I approached the duty manager and explained to him what had happened. The manager's response was that I should not have spoken to the security guard, I should have spoken directly to the manager himself. When I asked him what he was going to do, he replied that he would email the company that employed the security guard. There was no offer of an apology or any indication that what had happened was viewed as unacceptable or against company policy. Coincidentally, whilst I was speaking to the manager another female black customer commented that she had experienced that same kind of surveillance whilst shopping there that day. When I asked the manager what his thoughts were on the similar experience of another black customer, he informed me that he was busy trying to repair a fault with a self-scan checkout. Outside of the store, we were approached by a young black man who said that he had witnessed what had occurred in the store, and that he too had been followed around the same store by security guards in the past. Three random black customers, all sharing the same experience of being stalked by security guards around the same store. I don't think this is a coincidence. I think this store actively targets black customers.