He became outspoken in the House of Lords and the press as an advocate for those with physical disabilities and mobility issues.
His parents married in 1960 and divorced in 1978.
When Antony Armstrong-Jones died in 2017, David became the 2nd Earl of Snowdon.
The Snowdons were the iconic couple of the Sixties, the centre of a glittering circle of novelists, writers, actors, politicians, dancers, beauties, inventors.
Princess Margaret's daughter was as high as seventh in line to the throne, but now she's 24th in the line of succession.
The Earl of Snowdon, David Armstrong-Jones, is the son of the late Princess Margaret.