'Messrs. Yarrow and Hedley, of Blackwall, were running on the Thames at Henley on Wednesday and Thursday an excellently constructed twin-screw launch; she is 40 ft. in length, 6 ft. in breadth, and 7-horse power, and is built expressly for the navigation of the upper waters of the Thames… The run from Messrs. Yarrow and Hedley's Works at Blackwall up to Henley in this launch occupied 17 hours, including about four and a half hours for stoppages in passing through the 17 locks from Teddington to Hambleton, and other delays, giving an actual running time of twelve and a half hours for the distance of 73 miles, giving a speed of nearly 6 miles an hour, against a 3 mile tide and stream.'