This was underpinned by an agreement between the British Admiralty and Vickers, granting the shipbuilders the exclusive right to build Admiralty-designed submarines in private shipyards.

A foreign design would also circumvent the agreement with Vickers, allowing other British shipbuilders to get involved, which would increase construction capacity.

[3] Keyes appointed a six-man Submarine Development Committee to study foreign designs and provide recommendations.

[5] Accordingly, in August 1911 four British officers travelled to La Spezia in north-west Italy to visit the FIAT-San Giorgio works, where they inspected two Medusa-class submarines, designed by Cesare Laurenti.

[7] Four months later, in December, the Royal Navy placed an order with Scotts' of Greenock, Scotland for one submarine to a similar design, to be powered by two Scott-FIAT diesel engines.

[7] Scotts, who had tendered £50,000 (equivalent to £6,400,000 in 2023)[8] for the contract, held a license from FIAT-San Giorgio to build the submarines for the British market.

[7] The S class were coastal submarines, designed for the defence off the British coast, rather than operating in foreign waters.

[11] This made them a similar size to the existing British C-class submarine, though the design differed quite significantly.

The submarine was stranded for three days before they sighted a German fishing trawler, Ost, which they commandeered and used to tow S1 some 500 kilometres (300 miles) back to the United Kingdom.

[18] Gardiner and Grey reject the latter claim, saying that "there is no apparent reason why boats with such a high reserve of buoyancy should be poor seaboats"; they instead suggest that the unpopularity of the S class was more likely due to "the general lack of familiarity with Italian practice and design".