But they’d heard nothing over the grinding of the prop shaft.

‘Leave your bags,’ the steward ordered as he grabbed the case containing the documents from Rosie’s hand and threw them back inside the cabin.

‘They’re important,’ Rosie said, as the queue moved forwards towards the steps.

‘Don’t be stupid, girl,’ the steward said unsympathetically, as he barged on through the passengers. ‘People are important.’

Life seemed increasingly cheap but Rosie knew he was right, as she looked back to make sure that Paul was still behind her.

The dive bomber had hit the Cardiff Bay less than five kilometres out of Bordeaux, in the broad channel that led from the port to the Atlantic Ocean. The ancient steamer was steadily tilting forwards as water poured through a hole in the bow.

As Rosie made it up the near-vertical steps and into the twilight, she looked along the deck and saw that the bow was already touching the waterline and the stern was way out of the water. The passengers stood on deck in their life jackets as the crew pulled tarps away from the lifeboats and began the clumsy process of lowering them over the side into a mercifully calm sea.

Below decks, the seawater reached the boiler room in the heart of the ship. As it rushed into the furnaces, the mass of water hit flaming coals and the result was superheated steam. Horrific screams echoed from below as men boiled alive and the extraordinary pressure ruptured one of the funnels and blew several deck hatches into the air.

Rosie grabbed Paul tight as the air filled with the tang of burning paint and hot metal. High above, a German Stuka had started a near vertical bombing run. Its bombs missed by more than twenty metres, but a series of underwater explosions threw the ship to one side. The hull levelled off, but this was a false dawn and a mass of water rebounded towards the front of the ship and dragged the bow underwater.

There was a deathly grinding noise as the front of the ship sank. Screams came from all around as people charged towards the stern, grabbing whatever they could hold on to as the angle of the deck grew steeper.

Many seemed to hope for a miracle, but Rosie was a realist and she knew they were going down.

‘We either jump now or go down with it,’ she shouted, grabbing her brother by his life jacket and straddling the handrail as adults charged past in one direction, whilst an increasing amount of debris barrelled down the deck towards them.

The hull had been more than fifteen metres out of the water when Paul and Rosie boarded, but the old steamer was plunging like a torpedo and they touched water the instant they were over the handrail.