Lane-Fox was returned to parliament as one of two representatives for Helston in 1831. He became the sole representative after the 'Great' or 'First' Reform Act of that year reduced the low-electorate constituency to one seat. He lost the seat in 1835, and remained out of the House of Commons until 1840, when he was returned for Beverley in East Yorkshire. He lost the seat the following year and was re-elected to the Commons the year after as one of two MPs for Ipswich, Suffolk. In 1847 he was once again elected for Beverley, a seat he held until 1852.
Family
Lane-Fox married Lady Charlotte Mary Anne Georgiana Osborne, daughter of George Osborne, 6th Duke of Leeds, in 1826. She died in January 1836, aged 44. They had five children:
The family received rents of land and buildings for the duration of the lives of three of Lane-Fox's children, assigned by his cousin Francis D'Arcy-Osborne, 7th Duke of Leeds, mainly in the Cornish parishes of Breage, Camborne, Germoe, Ludgvan, St Erth and Wendron — which brought annual income of £5,000. On Elizabeth's death these freehold reversions reverted to the ownership of the then-heir of the senior branch, George Osborne, 9th Duke of Leeds. Sackville Walter Lane Fox after the death of his wife had a relationship with Charlotte Susannah Olding and they had two daughters the eldest Charlotte Alice Fox surname Olding was born 18 January 1850 and the younger Lucy Susannah Charlotte surname Fox born 27 March 1855. Charlotte Alice Fox Olding was born at 11 Burton Street London and was Baptised eleven years later as Alice Florence Marion Fox at St Saviour Jersey by The Rector William Corbet Le Breton who was the Father of Lillie Langtry - The Jersey Lily. Florence died 24 July 1926 as Florence Alice Marion Fox-Bryant Lucy Susannah Charlotte was born at 12 Hill Street Knightsbridge but her mother's address at the time was 17 Cowley Street Westminster. Lucy did not marry and died in Kensington in 1927. There are no marriage records for Sackville Walter Lane Fox and Charlotte Susannah Olding. Charlotte Susannah Olding does have two death certificates one as Charlotte Susannah Fox widow of Sackville Walter Lane Fox which was superseded by a death certificate in the name of Susannah Charlotte Olding.