His son Maurice Macmillan died three weeks later, making Stockton the heir to the new earldom, and he succeeded as a member of the House of Lords on his grandfather’s death at the end of 1986.

[5] However, he is not recorded as having spoken in any debates there,[6] and was one of the hereditary peers who lost their seats as a result of the House of Lords Act 1999.

Stockton has been an unsuccessful candidate sixteen times in the by-elections held among hereditary peers for a seat in the House of Lords, as of 2019.

There were three children from this marriage: On 23 December 1995, Stockton married Miranda Quarry (1947–2020), who had been the third wife of actor Peter Sellers.

After driving home from an event on 31 July, where he had drunk some wine, he swerved his Range Rover into parked cars, causing minor damage to the vehicles.