As a message carved in stone says "Copa'r Wyddfa, Yr ydych chwi yma, Y nes at y nefoedd" - "The summit of Snowdon, Here you are nearer, To heaven".

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He writes that after Michael Stone was imprisoned for the Milltown cemetery killings, Stone sent a message to veteran BBC cameraman Peter Cooper, who had captured the terrifying close-up footage of the attack.

BBC: Northern Ireland

Buck's urgent message is proof of the value of Twitter, Stone said.

CNN: Student 'Twitters' his way out of Egyptian jail