With 20107 & 20096 idling noisily underneath the footbridge on which I am standing, 20311 & 20314 slowly propel the new London Underground S stock unit to the far end of the Asfordby Depot, Old Dalby, on 28 August 2015. All four Class 20s had arrived with the underground stock as the 7X23 09:33 Derby Adtranz Litchurch Lane to Old Dalby.