A huge boring machine has started tunnelling beneath the Thames, as part of London's £180m transport system extension for the 2012 Olympics.
The machine, nicknamed Carla, weighs 540 tonnes
The 540-tonne machine started work on Monday at North Woolwich, south-east London, and will bore beneath the river at three metres per hour.
It will extend the Docklands Light Railway (DLR) from the existing King George V station north of the river.
Olympic shooting events will be held at the Royal Artillery Barracks, Woolwich.
Mayor Ken Livingstone was at Woolwich Arsenal on Monday morning, to take a look inside the 40ft (12m) deep tunnel shaft.
He said: "The extension will be a vital new transport link that will regenerate the local area and play an important role during the 2012 London Olympic and Paralympic Games."
The machine will dig about 115ft (35m) beneath the Thames and should take 15 months to reach its destination.
The 2.4km (1.5 mile) extension is due to open in 2009.
As it works, it will remove enough material to fill 40 Olympic-sized swimming pools, says Transport for London.
The DLR has recently completed another extension to London City Airport.