Paul Lamb, who was paralysed in a road accident will continue the right-to-die campaign, started by locked-in syndrome sufferer Tony Nicklinson.
Tony's wife Jane spoke to Daybreak, she said: "It was never just about Tony it was always about people like Tony, and I feel very strongly that people in that position should have the right to take their own life when they choose."
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Some 66 people have been killed after the plane they were travelling on crashed in southern Iran.
The letter calls for an end to harassment, abuse, and impunity in a world "ripe for change".
Police say that anyone who sees Whitehouse should not approach him, but instead call them on 999 and quote incident 23 of 18 February.