It was considered that 47 of these were up to date.
Around 270 British submarines were eventually deployed.
73 British submarines were lost in the war.
3,142 lives were lost.
One British submarine was lost for 7.8 ships sunk by British submarines.
British submarines sank 493 enemy merchant ships totalling about 1.5 million tons, around 134 warships, plus 34 submarines.
Another 35 warships and six submarines were damaged.
World War Two
BBC History of World War II
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