On May 25, 9:36*pm, Jamie Thompson wrote:
My understanding was that the ground it's located in was just
particularly difficult to build a station in, and as the ELL was
somewhat of a backwater, why expend silly money on the most expensive
part, namely the tunnelling out of the station box.

OK, that makes sense - but it does somewhat beg the question as to why
no-one had the foresight to see what was coming for the ELL. I guess
the simplest answer is that the JLE was designed before the ELL
extension in the form we see today was really envisaged.