Even the "firing point" is not known for certain, but it was probably a British submarine and Dr Malcolm McIntosh, chief of defence procurement at the Ministry of Defence, told the MPs, with masterly understatement, that it was "placed in some jeopardy".
Exactly what went wrong is something that the Ministry of Defence refuses to reveal; one MP on the Public Accounts Committee, which heard Dr McIntosh's evidence in November 1991, recalls seeing documents outlining what had happened, but not being allowed to keep copies.
The Ministry has reason to be embarrassed. Spearfish, the boomerang torpedo, whose problem was unpublicised until today, is just one in a long line of British defence disasters. Over the past 20 years, a variety of hugely expensive British defence systems have turned out to be late in service, over-budget, unreliable or just plain unworkable. And they all have one thing in common: they were developed by Britain's largest electronics company, GEC, under its managing director, Lord Weinstock.
The troubled systems include:
t The Tigerfish, the Spearfish's predecessor, which was still unreliable after 15 years of development.
t Radar systems for jet fighters and Royal Navy frigates that do not work properly.
t A pounds 270m unmanned spy plane which should have been ready three years ago but is still beset by problems.
t Britain's Airborne Early Warning aircraft system, based on the successful 1960s-vintage Nimrod, which could not distinguish between enemy planes and lorries on the A1. After more than pounds 1bn had been spent, it was thrown on the scrapheap. American Awacs aircraft were brought in to replace it.
Spearfish itself, designed to hunt down and destroy nuclear submarines with a complex sonar targeting system, was brought into service only in March last year, seven years behind schedule and pounds 175m over its pounds 885m budget. Its problems were not, presumably, confined to its boomerang effect: Dr McIntosh told MPs that, at that stage of its trials, it was "performing appallingly".
GEC's remarkable catalogue of defence project failures did not prevent Lord Weinstock and his company from taking over VSEL, builders of the Trident submarine, earlier this year and thus rivalling British Aerospace as Britain's biggest defence contractor.
Arnold Weinstock, as he was before his ennoblement, is reportedly fond of asking his directors: "Why are you spending my money?" After the Nimrod fiasco, the most famous and spectacular failure of all, the MoD started to ask the same question of his company.
It was partly GEC lobbying that persuaded the Government to develop Nimrod rather than buy the cheaper, more reliable Awacs system from the US. Nimrod, said GEC Avionics in 1977, was going to be the best early warning system that money could buy.
It was cancelled in 1986. By then, it had become an international laughing stock. To get it working to the original specification would have cost a further pounds 500m.
Then there was the Foxhunter radar system. This was to be used on RAF Tornado fighters. It was supposed to be capable of identifying up to 20 enemy planes more than 100 miles away while avoiding detection by enemy radar. But the tracking system was only 60 to 80 per cent effective; it was vulnerable to radar jamming; and it turned out to be too complex for the Tornado's missile system.
The finished product was so late that, by 1985, Tornado pilots were flying with concrete ballast in the noses of their jets to simulate the weight the radar should have taken up. Even in the Gulf war, six years later, the radars were unable to do what they were supposed to do. Fortunately, by the time the Tornados took to the air, the Iraqi air force had fled.
The Tigerfish torpedo - whose development was taken over by Marconi Underwater Systems, a GEC subsidiary in 1972 - also proved inadequate in war. During the Falklands conflict in 1982, HMS Conqueror, the submarine that sank the Argentine cruiser General Belgrano, was forced to use a Second World War vintage torpedo to ensure a "kill". Fewer than half the Tigerfish, it had been discovered, could get anywhere near their targets.
None of this has apparently dented the MoD's confidence in GEC. The company was commissioned to develop the Phoenix drone, a remote-controlled spy plane, designed to fly over battlefields and bring back photographs of enemy positions and artillery. But the plane is reported to damage its cameras each time it lands. Its delivery is now three years overdue.
In Spearfish's case at least the Ministry is now apparently convinced that the problems are over. Last December it announced a pounds 630m contract for GEC Marconi to supply and support Spearfish for the Navy. And one defence analyst specialising in underwater weapons said last week that, although the boomerang effect was probably caused by mechanical problems, many of the other difficulties with Spearfish had been created because its electronics were so sophisticated. The MoD was partly to blame, he added, because it had "changed the goalposts for this torpedo more than once".
GEC Marconi's side of the story, however, must remain untold. It declined to comment on tany of the its defence contracts. "We don't think there is any virtue in commenting on what has passed," a press officer said.Reuse content