'But forgive me, sir, is it Spain or Portugal?'

'Have you read the full text of the new Treaty with Bonaparte?'

'Yes, sir. At least, what was published in the Gazette. There might have been secret clauses...'

'There were none,' St Vincent said shortly. 'Did you see any reference to Trinidade?'

'No, sir, just Trinidad, which Spain loses and we keep.'

'Yes, one of the few places Bonaparte allowed us,' St Vincent said with the first indication of his own views about the terms of the treaty, although it was quite clear to Ramage that he welcomed the peace. 'Now, have you Trinidade placed in your mind?'

'Yes, sir. A thousand miles or so south of St Paul Rocks and Fernando de Noronha, and about the same distance west of St Helena.'

'Precisely. An isosceles triangle would have St Paul Rocks and Fernando de Noronha as its apex, Trinidade on the left of the base and St Helena on the right. Now, what strikes you about its position?'

'If it has water, then it is a perfect place for the King's and John Company ships to call on their way to or from the Cape of Good Hope. At present - or, rather, in the war - the Honourable East India Company were very nervous of having their ships call at St Helena for water because both French national ships and privateers usually lurked close to it. Trinidade would be a good alternative.'

St Vincent nodded with his rare wintry smile. 'And a good rendezvous for the trade bound to or from Rio de Janeiro, Montevideo and Buenos Aires, as well as the Cape. It has water, by the way.'

'Who owns it, then, sir?' Ramage asked for the third time, guessing from the spelling it had been named by the Portuguese.

'No one,' St Vincent said. 'We used it occasionally in this late war and can claim to have captured it, but it belonged to Portugal before that. It is not mentioned in the Treaty.'

'So whoever notices the omission and gets there first. . .'

'Exactly,' St Vincent said. 'Speed and secrecy, my dear Ramage. You have a fast ship and a good crew. Now go and claim it for His Britannic Majesty.'

The Hydrographic Office was simply a small room: Dalrymple sat on one side of a table and his assistant, Walker, on the other. One wall was taken up with what appeared to be tall chests of drawers, the drawers being wide but shallow, and each labelled. A small table at the far end of the room was piled high with volumes which Ramage recognized as masters' logs, and he recalled a paragraph from the Regulations and Instructions concerning masters: 'He is duly to observe the appearances of coasts; and if he discovers any new shoals, or rocks under water, to note them down in his journal, with their bearing and depth of water.'

A conscientious master usually did better than that. Many were skilled with a paintbox, enjoying making sketches of unfrequented coastlines and preparing good line and wash illustrations. Often a master would make two sketches, one to go into his own collection of charts and views, the other to be inserted in his log, which had in due course to be sent to the Navy Office. One of Dalrymple's most difficult tasks, Ramage guessed, was getting logs from the Navy Office: the Navy Board had a reputation for losing documents. The few hundred yards from the Navy Office in Somerset Place to the Admiralty in Whitehall might well have been a few thousand miles.

Dalrymple was courteous. Few captains visited his office; usually he saw only masters, who were, officially, responsible for the actual navigation of a ship.

Yes, he said, he had a map of Trinidade, but not a chart. The map was in fact Spanish, and found on board a prize, which accounted for the Spanish spelling, with the final 'e'.

He went to his chests of drawers, pulled out the one labelled 'T', sorted through some papers and then extracted a rectangular sheet of parchment measuring about two feet by one. He blew dust from it and brought it to the table, where he wiped it again with a cloth.

'You see, the cartographer - I'd hardly call him a surveyor - was more concerned with drawing the voluptuous cherubs in the corners than details of the island. There's enough giltwork to cover a ship of the line's transom!'

Ramage stared at the map. The island reminded him of a mole. It sat diagonally southeast-northwest, with the northern coast, the back, almost a straight line, with no bays. There were several small anchorages on the south side formed by pairs of peninsulas sticking out like teats hanging down from the belly. He picked up a magnifying glass and began reading the Spanish references to the 'A', 'B', 'C' marks on the island itself.

The latitude and longitude were given, 20° 29' South and 29° 20' West. There were six hills, looking like sugar loaves in the centre of the island, and someone had pencilled in the heights in feet, the highest being nearly 1,500 feet and the lowest 850 feet. There was a small rivulet of fresh water on the north side and another almost opposite on the south. Three places were marked as possible positions for batteries while another could be a signal station. There was no date on the map; not one depth was shown in the waters round the island.

'What date was this drawn?'

Dalrymple shrugged his shoulders and glanced at Walker, who shook his head. 'At a guess from the style and decorations, I'd say about 1700. I suspect a privateersman had thoughts about using it as a base against the Rio de Janeiro and Buenos Aires trade. Or perhaps the Spanish government wanted to keep privateers out. Whoever it was took care against the map falling into the wrong hands.'

'The lack of soundings?'

'Yes, with that kind of detail of the land, normally I would have expected soundings. Someone did not want to encourage visitors.'

'There must be some dangerous reefs, otherwise the soundings would be of little importance.'

Dalrymple nodded and said: 'I was just thinking that. It's a rocky island, so one would expect deep water close in, with rocks and foul ground. As you can see, it's an island the size of Hyde Park put down in the South Atlantic and rarely visited by the King's ships. The masters of those that have been there did not bother to do any survey work.'

'Can you make a copy of this map?'

'Of course,' Dalrymple said. 'I'm sorry we don't have it ready, but we had no warning. Walker and I do the best we can to prepare charts we think might be needed, but you can see those logs . . .' he pointed to the other table. 'Now the war has ended and scores of ships will be laid up, you can imagine how many more logs will be arriving for us to examine.'

'Do you often find anything of consequence?'

Dalrymple shook his head. 'No. The masters with the interest and ability to help us never seem to go anywhere interesting. They spot a fall of rock or a new battery along the French Channel coast, but apart from your Mr Southwick they don't benefit us much.'

'Ah, you find Southwick's log of interest?'

'Yes - his are the best sketches of the coast of Tuscany. And the recent ones of the southwestern corner of Sardinia were invaluable.'

'And the Catalan coast, sir,' Walker added.

'Ah yes, and of course many places in the West Indies. The island of Culebra. Parts of Martinique - Diamond Rock, for example: his survey and line and wash sketches of the Diamond are among the best examples of a master's work that we have.'

'May I tell him that?'

'Indeed you may, my Lord; we would welcome a good survey of Trinidade, of course . . .'

Ramage recalled St Vincent's warning about secrecy, even though the First Lord had suggested the visit to the Hydrographic Office. 'If we ever visit it, I'll do my best. I was just curious about it.'

'Of course,' Dalrymple said politely. 'Well, that's what we're here for. I wish more captains and masters would make use of us - and send us copies of charts! It's a slow business, building up a library of the charts of the whole world - which is what I intend to do. Who knows, one day we might be able to print and issue our own charts, instead of masters having to copy anything they don't have in their own private collections.'