This is the footpath entrance to the Folly’s tunnel at the Salisbury Road (North) end.
Yes, the entrance. And it’s 2-way. I assume the bloody great No Entry sign is to try to stop the double-decker buses from going down it. It’s clearly not tall enough.
If the No Entry sign was on the corner of the curb, I could understand it. But it’s not, it’s the far side of the pavement.