Aerial photos seem to show the old route of the spur, now partially built over, heading directly to the Soar below. So presumably it was locked down somewhere, now not discernible.
P.S. See the later update in the extra information section which addresses John's original comment here.
Photograph taken by John Howarth on 22 July 2008 and was added to the database on Wednesday the 23rd of July, 2008
This photo is one of 3 of Footbridge over Disused Basin and Former Mill Race on the Grand Union Canal (Leicester Section - River Soar Navigation) [Previous | Next]