The Blitz had shown the vital importance of securing a good water supply and the dire consequences when it failed. NFS London firefighters practised large scale exercises securing a water supply and relaying, or delivering, that water to the crews at the fire. Here lines of hose are directed back into the river (an imaginary fire) having been fed by the water supplied from the same river. The exercise was undertaken at Ordnance Wharf, Blackwall, East London.