Mr McDonald, who became a familiar face on television screens during the conflict, confirmed that the destroyer HMS Sheffield had been abandoned after an Argentine air attack.
She was struck by an Exocet air-launched anti-ship missile from a Super Etendard aircraft.
HMS Sheffield was the first major casualty of the Falklands War and the attack killed 20 men and injured another 24.
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She foundered six days after the missile struck - the first Royal Navy ship to be lost in action since the Second World War.