In 1929, he made two copies of the Stone of Scone, a coronation stone originally used by Scottish monarchs, but taken by Edward I of England to Westminster Abbey in 1296. Gray stood unsuccessfully for the National Party at the Dunbartonshire by-election, 1932, then when it merged into the Scottish National Party (Scottish National Party) in 1934 became the Assistant Secretary of the new party. He stood for the Scottish National Party in Dunbartonshire at the 1935 United Kingdom general election and a 1936 by-election in the seat, although he received less than 10% of the vote on each occasion.
Disillusioned with the Scottish National Party, Gray joined the Progressives, an anti-Labour coalition, and in 1947 was elected to Glasgow City Council, representing Blythswood.
Gray retained his nationalist beliefs. In 1950, the Stone of Scone was removed from Westminster Abbey by Scottish nationalist activists.
lieutenant was damaged in the process, and MacCormick, who had been involved in the plot, delivered it to Gray"s stonemason business, where he arranged for his head stonemason to repair lieutenant The following year, Gray and Ian Hamilton left the stone at Arbroath Abbey to be returned.
In 1974, Margo Macdonald persuaded him to rejoin the Scottish National Party, but he died the following year.
Following his death, Marion claimed that he had not confirmed whether the Stone of Destiny was genuine, and that she was happy for the secret to die with him. However, Warwick Rodwell argues that a copy made by Gray would not have fooled experts, and that the claims of a forgery did not appear until the 1970s, making the story unlikely.