Ladder crossovers at Harrow South Junction

In fact it wasn't an embankment when trains ran along it. When the flyunder was constructed a retaining wall ran alongside the current westbound Uxbridge Line with the old High Level line running along the top. This retaining wall ran from the point where the tracks emerge from beneath the Main Lines to the point where the Westbound and High Level lines become level with each other. The western end of this retaining wall can still be seen with a railing running along the top.
The reason the High Level line was removed was, so I understand, because the foundations of the retaining wall were unstable and a section would have required complete reconstruction in order to allow trains to continue to run along the high level line. At the time it should be noted that trains to Uxbridge from south of Harrow could only use platforms 4 and run via the dip or platform 1 and run via the high level line.
The cost of rebuilding the retaining wall would have been considerable and presumably it was deemed cheaper to remove the high level line, demolish the unstable section of retaining wall, cut the High Level formation back to a gentle slope (giving today's appearance of an embankment) and install an additional crossover (No 112) to allow Uxbridge bound trains to use platform 3 at Harrow instead of Platform 1.

Here's a quick sketch of what I mean

JB Dip