Hi, Wheels; no, they didn't say when it would be capped, but I can't see any reason why they should keep it open. If you go on Monday, I'm particularly interested in the concrete drain access behind the skip. Pinzgauer has suggested that it may be so they can run the drainage from the right (Holborn Hill end) around the shaft, instead of over it, but if they are going to cap the shaft, they could do that at a level to be below the line of those pipes. Makes you wonder......
Anyway, good luck on getting down (but not the risky way)

Cheers, Chris.