Millions of people pass under the River Thames each day, by rail, road or foot. We take it for granted. Just two centuries ago, the idea of going under the river would have seemed fanciful. Today, there are 20 different ways open to the public, and at least 25 further tunnels that most of us can't access.
Now that the latest addition, the Silvertown road tunnel, has opened, we thought we'd set out a clear list and graphic of every possible way of passing beneath London's river.
Rail tunnels under the Thames
Total: 14
Tube lines: Only five of the 11 tube lines pass beneath the river: Victoria, Northern (twice), Bakerloo, Jubilee (four times) and the Waterloo & City lines. The oldest of these is the W&C, which was dug out between 1894 and 1898.
Elizabeth line: Not technically a Tube line, the Purple Train crosses the river in just one place, between the Royal Docks and Woolwich. Were it ever to go ahead, the long-planned-but-never-funded Crossrail 2 would add a new Thames crossing between Chelsea and Clapham Junction in the same class as the Elizabeth line.
Overground: The oldest tunnel of any kind beneath the river — indeed, the oldest beneath any navigable river — was started by Marc and Isambard Kingdom Brunel way back in 1825, though not completed until 1843. The so-called Thames Tunnel was initially for pedestrian use, but was later converted to rail. Today it carries the Windrush line, part of the here-ironically named Overground network.
DLR: The light railway becomes the subaquatic railway in two places: Greenwich and Woolwich. With any luck, we'll need to update this article in the 2030s, if the much-anticipated extension from Beckton to Thamesmead finally goes ahead.
HS1: Beyond the scale of the map, the High Speed rail link cuts beneath the Thames between West Thurrock and Swanscombe. This is the only rail tunnel under the Thames that is not under the control of Transport for London.
Road tunnels under the Thames
Total: 4 (or 7 if separate bores are counted individually)
Rotherhithe Tunnel: This is the most westerly place in London where you can drive your motor under the Thames. It is also the only tunnel under the Thames through which cycling is permitted (though not many brave the fumes). You can also walk through it. Nobody ever does this twice. This is now the only free tunnel for motor vehicles. It is also the only road tunnel with two-way traffic.
Blackwall Tunnel(s): Actually two separate one-way tunnels, spaced quite far apart, and opened 70 years apart. For the purposes of counting tunnels in this article, however, I'm considering them as one entity. As of April 2025, vehicles must pay tolls to use the crossing.
Silvertown Tunnel: London's newest sub-Thames crossing, right next to the cable car, opened in April 2025. The route also comprises two separate bores, with northbound and southbound traffic separated. As with Blackwall, cyclists are not permitted to pedal through the tunnels, but a dedicated cycle-bus service operates. No pedestrians allowed.
Dartford Tunnel: Beyond the frame of our diagram, the Dartford Tunnel is the most easterly public tunnel beneath the Thames. Like Blackwall and Silvertown, it is a twin-bore tunnel, on which tolls apply. It connects together the two ends of the M25, in parallel with the Queen Elizabeth II bridge (none of which are considered part of the M25, and so the orbital motorway is not a complete circuit).
Pedestrian tunnels under the Thames
Total: 2 (though see also the Rotherhithe Tunnel above)
Greenwich foot tunnel: A late-Victorian walkway beneath the Thames. It runs parallel to the DLR tunnel, connecting Island Gardens to Cutty Sark.
Woolwich foot tunnel: A very similar passage, opened 13 years after the Greenwich tunnel. It is slightly longer and creepier. Both tunnels suffer from lift problems. The north lift at Woolwich has been out of service since the summer of 2022. Drainage issues are also a frequent problem.
Disused and non-public tunnels under the Thames
Besides the public tunnels listed above, numerous inaccessible tunnels span the Thames. These are the ones we know about.
Total: At least 25
The Tower Subway: Arguably London's first Tube railway, the Tower Subway was dug in 1870 two decades before the first sections of the Tube network proper (the Brunels' Thames Tunnel might also claim the title, depending how you define 'Tube'). The dingy passenger cars were hauled between the Tower of London and Southwark by cable rather than direct electric power. The company soon went bust, and the tunnel was converted to pedestrian use. The opening of Tower Bridge in 1894 made the tunnel redundant. It has since been used for cables and pipes, and no public access has ever been granted. You can still admire the northern entrance — a drum-shaped building standing, appropriately, outside Subway.
Battersea Steam Tunnel: A number of tunnels fan out from the old Battersea Power Station. Most were concerned with bringing power to and from the station (some urban explorers recently got into these tunnels), and the water ring main also crosses here. However, the area also features a more unusual pipe. The so-called "Battersea Steam Tunnel" carried waste heat from the power station across the Thames to the Churchill Estate. This formed the country's first district heating system. It's still in operation today, although it is now fed from gas boilers on site rather than waste heat from across the water.
Old rail tunnels: The Bank branch of the Northern line does not follow the same route as when it first opened as the City & South London Railway back in 1890. A decade later, a new route with wider tunnels was bored under the Thames, bypassing the old King William Street station. The old tunnels remain under the Thames but are now inaccessible.
Another lost fragment of Northern line can be seen over on the Charing Cross branch. From 1914, the line terminated at what is now Embankment. Trains would turn around in a loop that partly extended under the Thames before doubling back. The loop became redundant when the line was extended further south. It was sealed off, but took a direct hit during the Second World War and was consequently flooded with Thames water. It's since been plugged and drained, but remains unused (apart from the northern-most section of the loop, which is not under the Thames). Ian has the full details.
Sewers: Almost all London's sewers stick to one side of the river. Typically, they're not deep enough to get under the Thames. The extravagant exception is the Thames Tideway sewer. Recently completed, this monumental infrastructure project features one of London's widest tunnels — more than twice the width of a Tube tunnel — which tracks the route of the Thames between Hammersmith and Limehouse. It intercepts sewage from older sewers to the north and south, to ensure that very little now ends up in the Thames.
Gas and power tunnels: London's power network is an oft-forgotten part of the subterranean labyrinth, but it is one we all rely on every day. The trunk power tunnels can be large affairs. Some are comparable to tube tunnels (~3 metre diameter vs 3.5 metre diameter), and easily wide enough to walk along. Far less information on the tunnels is in the public domain, for understandable reasons. However, enough is known to map the key tunnels beneath the Thames. Several gas pipes also span the Thames. The most recent was dug in 2017 between Chelsea and Battersea.
Thames Barrier tunnels: Finally, a little-known pair of tunnels runs beneath the Thames Barrier in east London. These are used for maintenance, and as a quick means to get between the otherwise isolated pontoons that make up the structure. I was given a tour back in 2015.
Did I miss any? In a position to give me a tour of any of the 'secret' tunnels? Drop me a line on [email protected]
