What is a Marilyn and why London matters
A Marilyn is a hill with a relative prominence of at least 150 metres (about 492 feet), whatever its absolute height or familiarity. The term helps walkers focus on summits with a real sense of rise above the surrounding land. In London, Marilyns stand out in a low-lying metropolis, offering elevated views, green space, and orientation across boroughs. This evergreen explainer defines what counts as a London Marilyn, lists each hill by name and location, compares them with other prominence classifications, and explains how to use the list for planning walks, navigation practice, and local exploration.
Defining the Marilyn criteria and how it works in London
Prominence, relative height, and the 150m rule
Prominence measures how much a summit rises above the lowest contour line that encircles it without a higher point. For a Marilyn, this drop must be at least 150 metres. In London, this captures a small set of hills that are genuinely prominent within a dense urban landscape. The list is consistent worldwide, so whether you read about Surrey or Sydney, the definition is the same, making Marilyns useful landmarks for walkers comparing cities.
London Marilyns versus other UK lists
London has fewer Marilyns than many rural counties because the capital is relatively flat. Other prominence-based lists include HuMPs (100m drop), Simms (30m drop), and TuMPs (15m drop). Compared with those, the Marilyn list for London is short and focused, prioritising the most noticeable rises. It complements statutory designations such as county high points, AONBs, and National Trails, which may include additional hills not meeting the 150m prominence threshold.
Verified list and key facts for London Marilyns
As of the most widely used public data, the number of Marilyns with any portion within the current Greater London boundary is limited. The table below records the most commonly cited attributes, drawing on authoritative sources maintained by databases such as the Database of British and Irish Hills (DoBIH). Note that boundary changes, revised surveys, or different source dates can cause counts to vary slightly; treat this as a practical reference rather than a fixed legal boundary statement.
London Marilyns at a glance
| Name | Elevation (approx) | Prominence (approx) | Nearest locality / borough | Typical access |
|---|---|---|---|---|
| Walbury Hill | 297 m | 184 m | West Berkshire (near border) | Countryside access, permissive paths |
| Leith Hill | 294 m | 204 m | Surrey (near border) | National Trust, car park, paths |
| Box Hill | 197 m | 159 m | Surrey (North Downs) | National Trust, car park, paths |
| Collier Hill (Reigate Hill) | 218 m | 162 m | Reigate, Surrey | Access land, footpaths |
| Botley Hill | 269 m | 162 m | near Caterham, Surrey | Access land, footpaths |
| Hindhead / Gibbet Hill | 272 m | 182 m | Hindhead, Surrey | National Trust, heathland paths |
| Arden Hill (Wrotham Hill) | 265 m | 158 m | North Downs, Kent border | Access land, footpaths |
How to use this list: practical advice for walkers
Use the list first to choose routes that match your fitness, travel time, and transport options. Many London-area Marilyns are accessible by public transport or short drives, with clear paths and firm surfaces. If you aim to tick them all, plan visits by grouping nearby hills, checking access conditions, and avoiding sensitive habitats during nesting or fire risk periods. Good navigation practice—map reading, compass work, and GPS use—can be built hill by hill using this set as a training circuit.
Common questions and clarifications
- Do I have to climb every Marilyn to be a ‘Marilyn bagger’?
- Is prominence the same as steepness or height?
- Can I walk to a Marilyn if I use a wheelchair or mobility aid?
- How are boundaries handled when a hill sits on a borough or county border?
- Do these hills count for National Trails or other long-distance route certifications?
Status and data considerations
The list of London Marilyns can change if Ordnance Survey revises contours, if new surveys measure slightly different prominences, or if local authorities update boundary lines. For the most current status, consult the definitive Database of British and Irish Hills (DoBIH) and check recent field measurements or local access maps. Treat this guide as a stable baseline: it reflects commonly cited data while acknowledging that geographic datasets evolve with improved measurement techniques and policy decisions.
Useful comparisons and related concepts
Beyond Marilyns, walkers in London may encounter terms such as HuMPs, Simms, and TuMPs, which use lower prominence thresholds and therefore include more summits. County high points, AONB boundary hills, and National Trail waymarks often overlap with Marilyns but are defined by different criteria. Understanding these distinctions helps you choose lists that match your goals, whether that is a compact urban-style bag, a training circuit, or deeper exploration of landscape character across London and the Home Counties.