Peter St Clair-Erskine, 7th Earl of Rosslyn

Scottish nobleman (born 1958)

Peter St Clair Erskine, 7th Earl of Rosslyn, (born 31 March 1958), known professionally as Peter Loughborough, is a Scottish peer and police officer. He is Lord Steward of the Royal Household and Personal Secretary to Their Majesties, as well as a former Metropolitan Police Commander. The Earl's lands include Rosslyn Chapel.

Lord Rosslyn was educated at Ludgrove School, Eton College and the University of Bristol. He inherited his titles in 1977, and took his seat in the House of Lords on 15 January 1980. Ahead of the passage of the House of Lords Act 1999 which excluded most hereditary peers he was elected as one of the 28 peers in the Crossbench group who were to remain in the House of Lords. As of 2022, in 43 years in the House of Lords he had only spoken once and voted five times, each in relation to reform of the Lords.

Rosslyn joined the Metropolitan Police Service in 1980 on the recommendation of his third cousin Lord Strathnaver, From 2003 to 2014, he was head of the Royalty and Diplomatic Protection Department (since amalgamated into Protection Command). He received the King's Police Medal (then the Queen's Police Medal) in the 2009 New Year Honours and was reputedly the Queen's "favourite policeman". In March 2014, Lord Rosslyn was appointed as Master of the Household to The Prince of Wales, and The Duchess of Cornwall at Clarence House. On 22 February 2023, he was appointed Lord Steward of the Household, succeeding the 17th Earl of Dalhousie, and Personal Secretary to Their Majesties by Charles III. In this role, he took part in the 2023 Coronation.

He married Helen Watters in 1982 and they have two sons and two daughters, including actress Lady Alice St Clair Erskine. Lady Rosslyn runs the London Original Print Fair.