This is a highly specialist skill with high tech kit, a lot of water with specials none toxic cutting agent.
Video coming soon
TS Trenching drill under rivers and large roads like the A6 where there are multiple amenities running along them. Basically Swinny and his team set off 20m back from the edge and drill underground changing angle every section by 12.5 degrees. The B4MS duct under the A6 is 3.5 m deep and confidently missing the BT, Gas Main, Water Main.