Originally Posted by
terrain safe
I think you actually mean this:- "Unless specific procedures have been approved by the CAA, a landing aircraft shall not be permitted to cross the beginning of the runway on its final approach until a preceding aircraft, departing from the same runway, is airborne."
Yep, I was referring to the ICAO version. The one you quote (CAP 493) looks like the CAA's interpretation of the ICAO Doc 4444.
Still doesn't answer the separation question though.