My humble take: it's actually not meant to be an arrow - although it does indeed look like one - but the part of the embedded Union Jack that lights up.
I mean, that’s not a humble take, that’s what the article is about. That the use of the Union Jack has had the side effect of making the lights into arrows, but on the wrong side (when seen as arrows, which is a natural interpretation). Not that they were intended to be arrows.
