Finally Queen Mary was complete. Departure day was chosen as Tuesday, 24th March 1936, to take advantage of the high spring tide to help her down the Clyde. Minimum fuel was loaded, and only the two forward life-boats were fitted. Queen Mary was kept as light as possible, even though the channel had been dredged.  Thousands of local people gathered, local shops closed, and schoolchildren were given the day off.

At 9.30am, Queen Mary gave four blasts on her siren. The Blue Peter was hoisted at the foremast, and at the main flew John Brown’s houseflag. Tugs moved in and at 9.45am began to ease the liner out from the basin. Five local  ‘Flying’ tugs were used, plus Romsey, specially brought up from Southampton, and Paladin, from Anchor Line. Paladin and Flying Eagle took up forward positions, with Romsey and Flying Falcon aft. Flying Spray, Flying Kite and Flying Foam assisted alongside where needed.

Jointly they pulled Queen Mary, stern first, into the Clyde, before swinging her head round to face seaward. Some twenty minutes of delicate manœuvring was needed. Two local Clyde pilots, Duncan Cameron and John Murchie, were in joint command. Queen Mary slowly headed down river, under her own power. The tugs stayed in close attendance, and were used primarily for guiding the liner through the narrow channel.

As she approached Dumbarton Bend near Dalmuir, Queen Mary was caught by the freshening wind and swung across the river. Her stern caught briefly on the South Bank, but the tugs quickly pulled her off. She briefly grounded a second time but again without damage. Both times were, however, sufficient to be listed at Lloyds. Travelling at between six and seven knots, it took Queen Mary about four hours to cover the fourteen miles to reach open water, off Gourock, arriving at 2.10pm.

As she arrived she passed the burnt-out L’Atlantique, waiting to head upriver to the shipbreakers.
For the next two days Queen Mary was anchored off Gourock. Tests and trials were conducted on much of her equipment, and the lifeboats were fitted. At night she was fully floodlit. Further compass adjustments were made, anchor tests were conducted, and more fuel was loaded. Then, in the early hours of Thursday morning, she raised her anchors and sailed south, for Southampton.