Mrs Thatcher then had the Belgrano sunk to ensure there would be no negotiated withdrawal, it was an argentinian WW2 ship that was outside of the exclusion zone and sailing away from the islands.
Not the old outside the exclusion zone chestnut.
Exclusion zones are for the benefit of neutral vessels, not those belonging to countries at war. The captain of the Belgrano agrees his ship was a legitimate target, as did the Argentine government in 1994.
Though the ship was outside the 200-mile exclusion zone, both sides understood that this was no longer the limit of British action — on 23 April a message was passed via the Swiss Embassy in Buenos Aires to the Argentine government, it read:
“In announcing the establishment of a Maritime Exclusion Zone around the Falkland Islands, Her Majesty’s Government made it clear that this measure was without prejudice to the right of the United Kingdom to take whatever additional measures may be needed in the exercise of its right of self-defence under Article 51 of the United Nations Charter.
In this connection Her Majesty’s Government now wishes to make clear that any approach on the part of Argentine warships, including submarines, naval auxiliaries or military aircraft, which could amount to a threat to interfere with the mission of British Forces in the South Atlantic will encounter the appropriate response.
All Argentine aircraft, including civil aircraft engaged in surveillance of these British forces, will be regarded as hostile and are liable to be dealt with accordingly.”