The A31 is a major trunk road in southern England that runs from Guildford in Surrey to Bere Regis in Dorset. Its most well known section is the Hog's Back, a hilly ridge forming part of the North Downs, in the Surrey stretch between Guildford and Farnham.

Guildford is a town in west Surrey, England, around 27 mi (43 km) south-west of central London. As of the 2011 census, the town has a population of about 77,000 and is the seat of the wider Borough of Guildford, which had around 145,673 inhabitants in mid-2022 est. The name "Guildford" is thought to derive from a crossing of the River Wey, a tributary of the River Thames that flows through the town centre.