WORK on the second section of the Channel Tunnel Rail Link has reached a key stage. A 95-metre-long boring machine has started tunnelling its way under the River Thames in Swansombe towards Essex.

The 1,100-tonne machine began a 2.5km drive which will take about eight months. It will progress at a rate of 85 metres per week. An 8.15-metre diameter cutter head will slice through alluvium, gravel and chalk up to 40 metres below the river's surface.

As it travels forwards, it will place 33,000 concrete ring segments behind it to reinforce the tunnel. A total of 280,000 cubic metres of spoil will be removed. When section two is complete, the rail link will boast a new international passenger station at Ebbsfleet with services running from 2007.

Rail Link Engineering's contract manager, Tony Bermingham, said: "This is the first major tunnel to be dug under the river for over 20 years and we have learned many lessons from those who have gone before us. The tunnel boring machine has been purpose-built for this job and we have every confidence we can play our part in delivering this leap forward in British railway history."

Section one - the 46 miles between the Channel Tunnel and Fawkham Junction - is nearly 90 per cent finished. The completed rail link will halve journey times from central London to the Channel Tunnel.