Capper was particularly zealous in carrying out his duties during his first few years as Superintendent and was evidently keen to make a good impression on Lord Sidmouth, the Home Secretary. Sidmouth, who was the former Henry Addington, was a man of considerable influence. Educated at Winchester and Oxford, he had been an MP, Speaker of the House of Commons, first Lord of the Treasury, Chancellor of the Exchequer and President of the Council. He had been created Viscount Sidmouth in 1805 and had been Home Secretary since 1812. Capper had received from Sidmouth a detailed list of instructions which set out his responsibilities, and those of his staff. The instructions laid down how the convicts were to be treated, how many hours they were to work, how they were to be clothed, and their daily allowance of food. There was a strong emphasis on good discipline and cleanliness. Hammocks were to be taken down each morning and aired, the decks to be washed twice a week and swept every morning and afternoon. The surgeons appointed to the convict ships must 'inquire into the mental state as well as the bodily state of every sick person' and render the necessary assistance. The chaplains assigned to each ship must read prayers and preach a sermon every Sunday and visit every prisoner who requested spiritual aid.
The instructions to Capper emphasised that all healthy convicts must be sent on shore every day to labour. Following an inspection of his new domain, Capper despatched a report to Lord Sidmouth on 16 October 1815 in which he noted that there was no useful employment for those convicts imprisoned in the Portland Hulk in Langstone Harbour. Moreover the hulk was so rotten that it was not worth carrying out any alterations to its accommodation. He pointed out that there was at least four years' worth of work to be carried out in the dockyard at Sheerness and he therefore recommended that the 450 convicts on the Portland Hulk should be transferred to another ship at Sheerness. He suggested that the Lords of the Admiralty be requested to supply a suitable ship and he went on to make a specific recommendation: 'The class of ship, which I take the liberty of observing as most suitable for this service, would be a seventy-four, of about the same dimensions as the Bellerophon in the river Medway being of easy draft of water and lofty between decks.'
These words were to decide the fate of the Bellerophon. She was now twenty-nine years old. She had seen more than her fair share of action but she was capable of many more years of active service. The report on her sailing qualities completed by her captain in 1812 had found her to be a strong and well-built ship with no unusual symptoms of weakness. She had performed 'very well' or 'uncommonly well' on all points of sailing and her rate of sailing compared with other ships was 'in general superior'. But she was surplus to requirements. With Napoleon safely incarcerated on a remote island in the South Atlantic and with every prospect of a lasting peace coming out of the negotiations in Paris, Britain no longer needed a wartime navy.
At the time of Trafalgar in 1805 the navy had 241 ships of 20 guns or more (first to sixth rates), 310 smaller vessels in sea service, and some 90,000 seamen and 30,000 marines. By the summer of 1815 the numbers of men had dropped to 70,000 seamen and 20,000 marines but there were still 182 ships of more than 20 guns and 233 smaller vessels on the books. The Admiralty could no longer justify the expense of paying and victualling this number of sailors, nor could it justify maintaining the wartime level of warships. Of the twenty-eight ships which had taken part in the Battle of Trafalgar, ten had already been hulked or broken up, including the Téméraire, which had become a receiving hulk at Sheerness in 1813.
The Admiralty and the Navy Board had never been sentimental about old ships, however illustrious, and so Mr Capper got his way. The ship which had once been called 'the Flying Bellerophon' was condemned to spend the next ten years of her life as a convict hulk. But first she had to be converted from a warship into a floating prison. In his report Mr Capper had particularly requested that he be allowed to supervise the fitting out of the ship and asked that she be brought into dock at Sheerness for that purpose. In December 1815 the Bellerophon was towed into the dock and work began on preparing her for her new role.
It took the shipwrights, carpenters and blacksmiths of the dockyard nine months to carry out the necessary alterations. Iron grilles were fitted in all the gunports on the upper deck and the gun deck, and small additional ports were created on the orlop or lower deck which were likewise fitted with grilles. In a 74-gun ship loaded with guns and ballast, the orlop deck was below the waterline and was used as a storage area, but on a convict hulk floating high in the water it provided an additional deck for the accommodation of prisoners. Being immediately above the bilges it was a foul-smelling and airless place and was allotted to the worst of the prisoners. In place of the precarious steps used by the sailors to enter and leave the ship a permanent gangway was constructed down one side of the ship. This led down to a landing stage at water level. Two wooden huts were built on the foredeck, one of them for the storage of hammocks and the other to be used as a laundry. Beside them was erected a large crane to facilitate the loading of water, provisions and stores. A platform was built above and behind the figurehead and on this was constructed a shed which formed a wash house and toilet for the prisoners.
While the alterations above deck entirely altered the outward appearance and character of the ship, the alterations below deck were even more drastic. In the first generation of convict ships the prisoners were simply locked down below decks at night. There was no adequate supervision and no attempt to separate young boys from grown men, which inevitably resulted in the physical and sexual abuse of those unable to defend themselves from the more violent and predatory prisoners. By the time that the Bellerophon went into dock for fitting out, it had been agreed that the interior layout of convict ships should allow for visual supervision of the prisoners by the warders at night, and that the prisoners should be locked into cells holding no more than eight men in each cell. In effect this meant creating two lines of iron cages down the side of each deck with a corridor down the middle. The result was similar to that of the lion house or monkey house in a traditional zoo, a resemblance that was remarked upon by visitors to the convict hulk Defence at Woolwich in the 1840s:
On reaching the top deck we found it divided by strong iron rails (very like those in the zoological gardens, which protect visitors from the fury of the wild beasts) from one end to the other, into two long cages as it were, with a passage between them. In this passage a warder was pacing to and fro, commanding a view of the men, who were slung up in hammocks, fastened in two rows, in each cage or compartment of the ship.
There were eighteen cells or cages for prisoners on the orlop deck, twelve on the lower deck and twelve on the upper deck. The supervising staff had their quarters in the stern where the Bellerophon's officers had recently been accommodated. There were separate cabins for the first mate, the second mate, the third mate, and the steward. There was a cabin set aside as a surgery and a room for the chaplain. The warders shared a ward room below. The captain of the hulk, who acted as prison governor, was allotted the great cabin recently occupied by Captain Maitland and lent to Napoleon during his three-week stay on the ship. There is no record of the appearance of the cabin at this period but the visitors to the convict hulk Defence were particularly struck by the contrast between the governor's quarters and the rest of the ship. According to one account, 'We next adjourned to the governor's comfortable breakfast-room, with its pretty stern-windows, and its light blue and white walls. The military salute of the convict-servant who entered from time to time, with his white apron about his loins, was the only reminiscence of the hulk as we sat at the morning meal.'