A crucial stage of the high-speed Channel Tunnel rail link - the first of two tunnels under the River Thames - is now complete.

Milly the Muncher Cruncher, the giant tunnel boring machine pictured above, completed the 1.5 mile-long tunnel. and has now returned to Swanscombe in north Kent to start the second tunnel.

The first tunnel was completed in seven months, ahead of schedule.

On its journey the nine-yard-diameter cutter sliced through alluvium, terrace gravels and chalk at a depth of up to 40 metres below the surface of the river.

As the train travelled forwards it placed 33,000 concrete ring segments behind it to reinforce the tunnel.

The Thames tunnels are part of the 24-mile section 2 of the CTRL The line will run into London's St Pancras via new stations at Ebbsfleet in north Kent and Stratford in east London. Services begin running from the beginning of 2007.

Te £5.2billion CTRL will halve journey times from central London to the Channel Tunnel. The CTRL will allow high-speed services from commuters from Kent to central London.

London and Continental Railways has the public-private partnership contract with the Government to build and operate the CTRL. The project is partly funded by the European Union's Trans European network programme.

Information from Rail Link Engineering and Union Railways.