In fact, the Royal Navy’s anti-submarine tactics were, in the early stages of the war, miserably ineffectual. The British ships had no radar, and only a few were equipped with ASDIC. This formative submarine-detection device was housed in a dome beneath the hull of escort ships, like a great polyp. It sent out pulses of sound waves, which emitted a ‘ping’ that would produce an antiphonic ‘tong’ response if and when it struck a solid object within a 3,000-metre radius. This call and response would provide an accurate range and bearing. It was, however, notoriously unreliable in its formative
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