Testing of the ship's engines took place in June 1907 prior to full trials scheduled for July. A preliminary cruise, or "Builder's Trial", was arranged for 27 July with representatives of Cunard, the Admiralty, the Board of Trade, and John Brown aboard. The ship achieved speeds of over a measured at Skelmorlie with turbines running at 194 revolutions per minute producing 76,000 shp. At high speeds the ship was found to suffer such vibration at the stern as to render the second-class accommodation uninhabitable. VIP invited guests now came on board for a two-day shakedown cruise during which the ship was tested under continuous running at speeds of 15, 18 and 21 knots but not her maximum speed. On 29 July, the guests departed and three days of full trials commenced. The ship travelled four times between the Corsewall Light off Scotland to the Longship Light off Cornwall at 23 and 25 knots, between the Corsewall Light and the Isle of Man, and the Isle of Arran and Ailsa Craig. Over an average speed of 25.4 knots was achieved, comfortably greater than the 24 knots required under the admiralty contract. The ship could stop in 4 minutes in 3/4 of a mile starting from 23 knots at 166 rpm and then applying full reverse. She achieved a speed of 26 knots over a measured mile loaded to a draught of , and managed 26.5 knots over a course drawing . At 180 revolutions a turning test was conducted and the ship performed a complete circle of diameter 1000 yards in 50 seconds. The rudder required 20 seconds to be turned hard to 35 degrees.