Visitor figures at the Royal Navy Submarine Museum took a noticeable dip in the past year – but those people who did come spent more than in the past.

The annual report of the Gosport memorial and museum to the Silent Service for the 2002-03 financial year shows that, despite a few blips, it is in good health for the future.

Visitor numbers were disappointing, with 16 per cent fewer people choosing to tour the museum in 2002-03 than in the previous 12 months – a total of 64,100 in all.

The drop is attributed to a particularly good 2001, during which the Submarine Service celebrated its centenary and the new Holland I viewing gallery was unveiled with the newly-restored submarine in place.

The fall-off in interest in 2002-03 was balanced by tourists spending much more on gifts and souvenirs during their visits.

Other good news for the museum is the support it gets from schoolchildren – 4,000 a year now learn about the Submarine Service – and more than nine out of ten tourists rated the museum as ‘very good’ in an official survey.

Vice Admiral Sir Roy Newman, chairman of the museum’s trustees, said with plans for a new exhibition hall – the Fieldhouse building, in memory of the late former Flag Officer Submarines and First Sea Lord Admiral of the Fleet Lord Fieldhouse of Gosport – a revamp of HMS Alliance and the weapons gallery, the next few years would be dynamic.

“Once that is complete I believe that we will have fulfilled the dreams of those who started the museum in a single metal cabinet over the submarine church in HMS Dolphin,” he added.

• The subject of the Submarine Museum’s Christmas card this year is the earliest submarine – that is, a boat that can be submerged and then propelled underwater – on record, although an even earlier mention of such a vessel occurs in the writings of Englishman William Bourne.

The Christmas card features Dutch physician Cornelis van Drebbel demonstrating his ‘Submarine Boat’ to King James I against the skyline of London in 1620, dominated by the original St Paul’s Cathedral, which was destroyed in the Great Fire of 1666.

But in a book published in 1578, Bourne gives a remarkably accurate exposition of the principles that still govern the submarine in the age of nuclear propulsion.

All that is necessary to make a boat that will go under the water and then surface at will, he explains, is to construct it in such a way that the volume of water it displaces can be varied: “. . . any magnitude of body that is in the water, if that the quantity of bignesse, having alwaies but one weight, may be made bigger or lesser, then it shall swimme when you would, and sinke when you list . . .”

To vary the ‘bignesse’ was to make “the joints or places that doo make the thing bigger or lesser of leather; and in the inside to have skrewes to winde it in and also out againe . . .”

Bourne never put his theory to the test, but some have argued that had he implemented his plans with the same amount of detail he put into outlining them, he would have stood a good chance of success.

Decades later, van Drebbel built at least three submarines, and delighted Londoners with his demonstrations.

No contemporary drawings of them exist, but there are so many references to them that he may be regarded as ‘the father of submarines’.

One apparently contained a dozen rowers and still had room for passengers – including, reportedly on one occasion, James I himself, although this seems unlikely.

They appear to have been constructed of greased leather stretched over a wooden frame containing goatskin bags which could be filled with water for submerging and then squeezed out for surfacing.