The man nodded his agreement and set himself to row back to Buckingham’s ship while John flung himself on the bell and sounded the alarm. The sailors scrambled out of the waist of the ship, clutching their dinner – nothing more than a thin slice of rye bread and a thinner slice of French bacon.

‘Get me a light,’ John cried. ‘I need to signal to the ships to take that loose vessel up. The barrier is breached.’

‘I thought they had surrendered!’ the captain shouted as one of the men ran for a lantern.

‘They sent terms,’ John said. ‘His lordship is considering them.’

The captain turned and roared for a light and ordered the gunners to their posts. The signalling officer came running up with flaring torches. ‘Tell them to take up that ship,’ John said.

The man ran forward and started signalling. John, looking past him, suddenly saw a gleam in the dark water, a reflection.

‘What’s that?’

‘Where?’

‘In the water, beside that ship.’

One of the officers stared where John was pointing. ‘I can’t see anything,’ he said.

‘Hold a torch out!’ John ordered.

They held a torch low over the water and saw the dark shadow of a French barge, rowed swiftly towards the gap in the barrier.

‘To your places!’ the captain yelled. John raced to the bell and rang it again. The gun crew opened the hatches and ran back the cannon for priming and loading; the soldiers poured out on deck. Someone lit and threw a flare towards the dark water below and in its briefly tumbling light John saw a string of barges rowing steadily and confidently from the Papist camp around La Rochelle towards the fort of St Martin.

From the other end of the barrier of English ships he heard the bells ringing for action stations. A single cannon started pounding in the darkness and then he felt the timbers under his feet shake at the explosion and recoil of the guns on his own ship. The loose ship which should have been lashed into the barrier was swinging wildly out of control, the crew swarming to get sails up, and to get her under way so that she could rejoin the line. But through the gap she had left the barges were pouring, heading straight for the citadel.