I believe he was referring to arms with holes in them, i.e. from shooting drugs with needles. I.e. needle holes.
Thus, “4000 holes” are 4000 thousand people - which I believe is the capacity of the Albert Hall.
oops...meant “4000 people” NOT “4000 THOUSAND people”
anywho...the 4000 holes are 4000 people with drug needle holes in arms.