in 1791, as part of the campaign to promote the construction of the horncastle canal, the commissioners of the river witham asked the engineer william jessop to assess the state of the fossdyke navigation and the witham, with particular reference to the problems of navigating through lincoln, where the channel was restricted by a medieval bridge. he proposed two solutions; the first avoided the route through the city entirely, by utilising the course of the sincil dyke to the south, while the second involved lowering the bottom of the channel through the glory hole bridge, which was only deep at normal water levels. the commissioners had imposed a toll on all traffic passing under the bridge, but decided that a channel bypassing the city would have grave financial consequences. they opted for improving the existing channel and the work to remove the wooden floor, to lower the river bed under the bridge and to underpin its foundations was completed in 1795. the commissioners dropped the collection of tolls at the bridge, but the amount they received from traffic passing through the locks increased as the volume of traffic grew in response to the easier passage through the bridge.