Midday, and they weathered the Korfas headland. Asai was a stone’s throw off their starboard oar tips, and the wind was directly in their teeth.

Which proved to be altogether in their favour.

‘Ready about!’ Fra Tommaso screamed. Swan hadn’t really ever heard the old man stirred to emotion before – perhaps flares of anger, but nothing like this urgency. Swan was in his hammock, forward with the archers – he rolled out, grabbed his sword, and ran for the helm, feet pounding along the catwalk.

The oarsmen cursed, but those on the port side were already reversing benches. And behind him, the vessel’s sailors had the sail on the great yard, ready to be raised.

Swan leaped on to the command deck from the catwalk. Fra Tommaso pointed forward over the bow, and Swan turned.

There, framed against the strait, was a fleet that seemed uncountable – more than a hundred vessels of all sizes. In the van there were at least a dozen military galleys, and most of them had their sails up and their bows threw white waves as they came on.

‘The Turks,’ Fra Tommaso said.

Behind Swan’s shoulder, Peter grunted. ‘Son of a bitch,’ he said.

The Blessed Saint John turned like a dancer and had her main yard aloft and her great lateen full in the time it would take a pious man to repeat a single paternoster. And her clean hull and her beautiful lines paid off – in an afternoon’s run, she gradually buried the Turks below the horizon, and they docked at Rhodos without further incident – that is, without food or sleep for two days.

But two thousand professional soldiers could accomplish an immense amount of work in a day. When the Turkish fleet hove into view on the northern horizon, the towers had their hoardings up, and Swan had a brief instruction on the use of a light artillery piece. The noise it made on firing caused him to twist his ankle on a chunk of rubble, but he knew what it took to put several ounces of charcoal, saltpetre and sulphur into the iron tube.

The tube in question was attached to a frame of good Greek oak. The whole contraption looked like a candlestick bolted to a table.

Peter watched the whole performance with contempt. ‘What can it do that my bow cannot do?’ he asked. ‘Ah – it can explode and kill me. My bow cannot do this.’ He handed his master a beautiful Turkish bow and two quivers of arrows. ‘I found these for you. If your new rank doesn’t preclude a little archery.’

When the Turkish fleet came over the horizon in the hours after dawn, the garrison was resting, the walls were barely manned, and the ships were safely inside the fortified mole. The only men working were slaves and conscripted Greeks, who were toiling with picks under a sun already ferocious despite the season, improving the network of trenches behind the weakest portion of the wall.

Swan rose late, with the other Donats from his section of the fortifications who had stood guard or worked far into the night. He climbed the windmill nearest to the English bastion and from it he watched the Turks disembark.

Sir John Kendal, the senior English knight under the turcopolier, and the acting commander of the forces in the English bastion, came up the windmill and seemed surprised to find Swan watching the Turks. He nodded and leaned his elbows on the edge of the parapet.

‘Do they intend an actual siege?’ Swan asked, after a period of silence. ‘Sir?’ he added.

Sir John seemed on the verge of muttering a platitude, but he paused. ‘You’ve seen some fighting?’ he asked.

‘Yes, sir,’ Swan answered.

‘You’re the young hellion who gave Sir Kenneth the bruise on his neck?’ Sir John managed a thin-lipped smile.

‘Yes, sir.’

Sir John nodded. ‘Fra Tommaso speaks very highly of you. So you know they aren’t landing any artillery.’

That’s what I was getting at, Swan thought. ‘Yes, sir,’ he said.

‘It’s a razzia. A raid. They’ll burn our crops and kill our Greek peasants and sail away.’ The older knight shrugged.

Swan might have agreed, except that the men he was watching on the hillside opposite him were men he’d seen in Constantinople – sipahis, or elite cavalry. They had no horses, but they were the Sultan’s best assault troops, and Swan had a difficult time imagining that the Sultan had sent his best troops – noblemen’s sons, no less – to burn crops.

‘They seem very interested in our section of wall,’ Swan noted.

Sir John fingered his beard. ‘So they do.’

Swan decided to take the plunge. ‘Those men there – in the silvery armour – are sipahis. Noble cavalry. The Sultan’s own.’

Sir John raised an eyebrow. ‘Really?’ he asked. ‘I had no idea.’ He smiled the sort of smile that older men give to young enthusiasts who assume that older men have never seen or done anything themselves.

Swan was defensive. ‘I saw them in Constantinople,’ he said.

Sir John nodded. ‘I’ve been fighting them for my whole adult life,’ he said.

Swan went down the windmill, determined to keep his mouth shut in future.

Late afternoon of the first full day. Thus far, not a single man had been killed or wounded. The Turks had summoned the town, sending a messenger and shooting arrows with demands for immediate surrender on very lenient terms. The knights, of course, refused.

Shadows lengthened, and the word came along the walls that everyone was to watch carefully. Dawn and dusk were the times when both sides would try stratagems, alarms and surprises.

Swan was at his ‘frame’, as the little gonne was called. He and his three Burgundian gunners were the crew. The Burgundians were less fiery than they had been in the days before the siege. The Turkish camp was like a city, larger than Rhodos itself. The Turkish fleet was vast and seemed to cover every beach in every direction.

‘How many men do you think they haf?’ one of the Burgundians asked him. ‘Sir?’ he added.

They all sounded like Peter. Their English was pretty good – half of the Duke of Burgundy’s army was made up of Englishmen, and the language was a lingua franca, but among themselves they spoke Dutch.

Swan shrugged. He was in half-plate, with a chain shirt under and a fustian arming coat under that – he was very hot, and emptied every canteen of water that was brought to him. He now owned leg harnesses – courtesy of the order’s armoury – and they were polished and ready, lying on his narrow bed. He wore Alexandro’s thigh-high leather boots instead.

He wiped his face with a linen rag. ‘About twenty thousand, give or take a thousand,’ he said.

‘Christ crucified, we will all be horribly kilt,’ muttered the senior Burgundian, Karl. The man had the nose of a heavy drinker and something was wrong with his eyes.

Swan ignored him, although he wasn’t too happy himself. His burst of enthusiasm for the Church militant had landed him in this desperate outpost …

There were men moving on the hillside opposite.

Swan plucked his armet off his head and put it on the stone walkway. He leaned out over the crenellations and looked.

A pair of arrows leapt from bowmen hidden in the rocks near the beach. Swan saw the bows move and ducked back. A pair of light arrows struck the parapet.

‘Let’s fire,’ he said. He pointed at where a dozen Turks were pushing big siege shields.

Next to him, Peter suddenly stood up to his full height and loosed a shaft. He didn’t loose at the men with the bows, but at the small crowd huddled on the hillside opposite, with wicker shields – siege mantlets.

His arrows struck a mantlet and pierced it.

The Burgundians hung back, as if actually using the gonne frightened them.

Swan ladled powder into the bore and ran it down. Then put a heavy patch of raw cotton atop it and rammed that down, and finally pushed a one-ounce stone ball down – laboriously chipped from Parian marble, no doubt, he thought. He took a goose quill from the pouch on Karl’s waist, ignoring the man, and aimed the gonne as he’d been taught – as he would a bow, a little to the left of the target because of the wind, and a little high – he put bricks under the front legs of the frame. In the time he did this, Peter loosed nine arrows.