Leith Hill in the context of Walbury Hill

The River Wey is a main tributary of the River Thames in south east England. Its two branches, one of which rises near Alton in Hampshire and the other in West Sussex to the south of Haslemere, join at Tilford in Surrey. Once combined, the flow is eastwards then northwards via Godalming and Guildford to meet the Thames at Weybridge. Downstream the river forms the backdrop to Newark Priory and Brooklands. The Wey and Godalming Navigations were built in the 17th and 18th centuries, to create a navigable route from Godalming to the Thames.

The Wey drains much of south west Surrey (as well as parts of east Hampshire and the north of West Sussex) and has a total catchment area of 904 square kilometres (350 sq mi). Although it is the longest tributary of the Thames (if the Medway is excluded), its total average discharge is lower than that of the Kennet and Cherwell. The river morphology and biodiversity of the Wey are well studied, with many places to take samples and record data. The main tributary is the Tillingbourne, which rises on the western slopes of Leith Hill and flows westwards to join the Wey to the south of Guildford, between Shalford and Peasmarsh.

The River Tillingbourne (also known as the Tilling Bourne) runs along the south side of the North Downs and joins the River Wey at Shalford. Its source is a mile south of Tilling Springs to the north of Leith Hill at grid reference TQ143437 and it runs through Friday Street, Abinger Hammer, Gomshall, Shere, Albury, Chilworth and Shalford. The source is a semi-natural uninhabited area. The catchment is situated on sandstone which has a low rate of weathering. The Tillingbourne is 24 km (15 mi) in length.

Stane Street is the modern name of the 91 km-long (57 mi) Roman road in southern England that linked Londinium (London) to Noviomagus Reginorum (Chichester). The exact date of construction is uncertain; however, on the basis of archaeological artefacts discovered along the route, it was in use by 70 AD and may have been built in the first decade of the Roman occupation of Britain (as early as 43–53 AD).

Stane Street shows clearly the engineering principles that the Romans used when building roads. A straight-line alignment from London Bridge to Chichester would have required steep crossings of the North Downs, Greensand Ridge and South Downs. The road was therefore designed to exploit a natural gap in the North Downs cut by the River Mole and to pass to the east of the high ground of Leith Hill, before following flatter land in the River Arun valley to Pulborough. The direct survey line was followed only for the northernmost 20 km (12 mi) from London to Ewell. At no point does the road lie more than 10 km (6 mi) from the direct line from London Bridge to Chichester.