Grey was born at Millfield Hall, Glendale, in Northumberland and educated at Richmond Grammar School. The first public cause he adopted was the campaign to abolish slavery. In 1823 Thomas Clarkson entrusted him with the task of collecting petitions in the Border towns. Grey accompanied Lord Brougham in his celebrated anti-slavery tours in Northumberland in 1826 and seconded the great man's speeches with his own. He took part in the struggle for Catholic emancipation and in the agitation before the Great Reform Act of 1832, making a number of eloquent speeches on the hustings at Alnwick.
Grey retired from active politics in 1833 and thereafter ran the agricultural and mining estates of the Greenwich Hospital in Northumberland and Cumberland with notable success. He had originally farmed in North Northumberland and was a keen agricultural reformer. Baron Liebig, the founder of agricultural chemistry, came to see him at Dilston, where Grey had moved in 1835, and was pleased to see his own discoveries being practically applied to the improvement of Northumbrian crops. Grey was the father of the great social reformer Josephine Butler, who wrote his biography.