Hidden Treasure In Cavern Club Wall

A dear friend of mine sent a picture of the wall of the Cavern Club in Liverpool (she went to Prestatyn in May) and there is something nice near the plaque: a Queen brick near the ones with the Beatles' names! Has anyone who's visited seen this in person, and if so who was responsible for including it?

I have seen it, I took a photo of it which I have somewhere. It's quite a wall-it's oppositte the Cavern Club and part of the wall to the Cavern Pub in Mathew Street (yes, one 'T' in Mathew).