The solution, posed as part of the forward-thinking Finsbury amendments, was to put the Jubilee line between London Bridge and Stratford, the Docklands Light Railway excluding Bank and Stratford and the East London line excluding Shoreditch and Whitechapel into a new fifth quadrant. Hardly surprisingly, this solution was never accepted by CAMREC, although they became increasingly marginalised due to their tactics.
In the Holland Park 2000 ruleset, an alternative solution was found, and quadrant five no longer exists in its original form. The idea of dividing the map into five rather than four did in fact form part of the solution used, but the new solution was to create a new, central 'quadrant five'. While this has caused some problems of its own, it has provoked significantly less protest from CAMREC. It appears that they are more concerned right now with logical and semantic consistency (or, more than likely, with their own in-fighting) than with actual gameplay.
Mornington Crescent scholars are still evaluating the consequences of having a quadrant that coincides with a zone. Historically, zones and quadrants have always been orthogonal to one another. In particular, there are deep implications for the studies of advanced pickerings.