A 5km (3m) rail tunnel under the M4 and M25 would link Terminal 5 with Langley and Iver to the railway to the West.
So a tunnel for the rail link under the M25 before the M25 enters a tunnel to go under the new runway before a steep climb to get over the M4.
A lot of tunnelling jobs available, and a lot of water west of LHR.
