Tunnels under the Thames
There are many tunnels underneath the river Thames serving a variety of purposes from allowing pedestrians to walk under the Thames (Woolwich and Greenwich foot tunnels) to non public tunnels that carry telephone cables etc.
Starting in the east of London, they are as follows:
1. Woolwich Foot Tunnel
This connects North Woolwich with South Woolwich and is approximately 1700 feet long. Either end is served by a lift service during the day, after that you need to be able to manage the stairs!! Woolwich foot tunnel was built in 1912 after tireless campaigning by a local working class politician called William Crooks.
The north and south side entrances both have distinctive circular entrance halls. As the name suggests, this tunnel is open only to pedestrians
2. Blackwall Tunnel
The Blackwall Tunnel is actually 2 tunnels that run side by side linking Poplar on the north side with Greenwich on the south side of the Thames. Each tunnel is a dual lane in each direction however in each tunnel one of the lanes has height restricting poles that hang down from the ceiling to ensure that tall vehicles do not use that lane.
The southbound bore also has the facility to make it into a 2 way tunnel by invoking a contra-flow system in the rush hour. These tunnels are only for motor vehicles with no means of accomadating pedestrians (other than for emergency exits)
there is more to come on the subject of tunnels under the Thames